Privoxy 3.0.6 User Manual Copyright © 2001 - 2006 by Privoxy Developers $Id: user-manual.sgml,v 2.26 2006/10/24 11:16:44 hal9 Exp $ The Privoxy User Manual gives users information on how to install, configure and use Privoxy. Privoxy is a web proxy with advanced filtering capabilities for protecting privacy, modifying web page data, managing cookies, controlling access, and removing ads, banners, pop-ups and other obnoxious Internet junk. Privoxy has a very flexible configuration and can be customized to suit individual needs and tastes. Privoxy has application for both stand-alone systems and multi-user networks. Privoxy is based on Internet Junkbuster (tm). You can find the latest version of the Privoxy User Manual at http:// www.privoxy.org/user-manual/. Please see the Contact section on how to contact the developers. ------------------------------------------------------------------------------- Table of Contents 1. Introduction 1.1. Features 2. Installation 2.1. Binary Packages 2.1.1. Red Hat and Fedora RPMs 2.1.2. Debian 2.1.3. Windows 2.1.4. Solaris, NetBSD, FreeBSD, HP-UX 2.1.5. OS/2 2.1.6. Mac OSX 2.1.7. AmigaOS 2.1.8. Gentoo 2.2. Building from Source 2.3. Keeping your Installation Up-to-Date 3. What's New in this Release 3.1. Note to Upgraders 4. Quickstart to Using Privoxy 4.1. Quickstart to Ad Blocking 5. Starting Privoxy 5.1. Red Hat and Fedora 5.2. Debian 5.3. Windows 5.4. Solaris, NetBSD, FreeBSD, HP-UX and others 5.5. OS/2 5.6. Mac OSX 5.7. AmigaOS 5.8. Gentoo 5.9. Command Line Options 6. Privoxy Configuration 6.1. Controlling Privoxy with Your Web Browser 6.2. Configuration Files Overview 7. The Main Configuration File 7.1. Local Set-up Documentation 7.1.1. user-manual 7.1.2. trust-info-url 7.1.3. admin-address 7.1.4. proxy-info-url 7.2. Configuration and Log File Locations 7.2.1. confdir 7.2.2. logdir 7.2.3. actionsfile 7.2.4. filterfile 7.2.5. logfile 7.2.6. jarfile 7.2.7. trustfile 7.3. Debugging 7.3.1. debug 7.3.2. single-threaded 7.4. Access Control and Security 7.4.1. listen-address 7.4.2. toggle 7.4.3. enable-remote-toggle 7.4.4. enable-remote-http-toggle 7.4.5. enable-edit-actions 7.4.6. ACLs: permit-access and deny-access 7.4.7. buffer-limit 7.5. Forwarding 7.5.1. forward 7.5.2. forward-socks4 and forward-socks4a 7.5.3. Advanced Forwarding Examples 7.5.4. forwarded-connect-retries 7.6. Windows GUI Options 8. Actions Files 8.1. Finding the Right Mix 8.2. How to Edit 8.3. How Actions are Applied to URLs 8.4. Patterns 8.4.1. The Domain Pattern 8.4.2. The Path Pattern 8.5. Actions 8.5.1. add-header 8.5.2. block 8.5.3. content-type-overwrite 8.5.4. crunch-client-header 8.5.5. crunch-if-none-match 8.5.6. crunch-incoming-cookies 8.5.7. crunch-server-header 8.5.8. crunch-outgoing-cookies 8.5.9. deanimate-gifs 8.5.10. downgrade-http-version 8.5.11. fast-redirects 8.5.12. filter 8.5.13. filter-client-headers 8.5.14. filter-server-headers 8.5.15. force-text-mode 8.5.16. handle-as-empty-document 8.5.17. handle-as-image 8.5.18. hide-accept-language 8.5.19. hide-content-disposition 8.5.20. hide-if-modified-since 8.5.21. hide-forwarded-for-headers 8.5.22. hide-from-header 8.5.23. hide-referrer 8.5.24. hide-user-agent 8.5.25. inspect-jpegs 8.5.26. kill-popups 8.5.27. limit-connect 8.5.28. prevent-compression 8.5.29. overwrite-last-modified 8.5.30. redirect 8.5.31. send-vanilla-wafer 8.5.32. send-wafer 8.5.33. session-cookies-only 8.5.34. set-image-blocker 8.5.35. treat-forbidden-connects-like-blocks 8.5.36. Summary 8.6. Aliases 8.7. Actions Files Tutorial 8.7.1. default.action 8.7.2. user.action 9. Filter Files 9.1. Filter File Tutorial 9.2. The Pre-defined Filters 10. Privoxy's Template Files 11. Contacting the Developers, Bug Reporting and Feature Requests 11.1. Get Support 11.2. Reporting Problems 11.2.1. Reporting Ads or Other Configuration Problems 11.2.2. Reporting Bugs 11.3. Request New Features 11.4. Other 12. Privoxy Copyright, License and History 12.1. License 12.2. History 12.3. Authors 13. See Also 14. Appendix 14.1. Regular Expressions 14.2. Privoxy's Internal Pages 14.2.1. Bookmarklets 14.3. Chain of Events 14.4. Troubleshooting: Anatomy of an Action 1. Introduction This documentation is included with the current stable version of Privoxy, v.3.0.6. ------------------------------------------------------------------------------- 1.1. Features In addition to the core features of ad blocking and cookie management, Privoxy provides many supplemental features, that give the end-user more control, more privacy and more freedom: * Integrated browser based configuration and control utility at http:// config.privoxy.org/ (shortcut: http://p.p/). Browser-based tracing of rule and filter effects. Remote toggling. * Web page filtering (text replacements, removes banners based on size, invisible "web-bugs", JavaScript and HTML annoyances, pop-up windows, header manipulation, etc.) * Modularized configuration that allows for standard settings and user settings to reside in separate files, so that installing updated actions files won't overwrite individual user settings. * HTTP/1.1 compliant (but not all optional 1.1 features are supported). * Support for Perl Compatible Regular Expressions in the configuration files, and generally a more sophisticated and flexible configuration syntax over previous versions. * Improved cookie management features (e.g. session based cookies). * GIF de-animation. * Bypass many click-tracking scripts (avoids script redirection). * Multi-threaded (POSIX and native threads). * User-customizable HTML templates for all proxy-generated pages (e.g. "blocked" page). * Auto-detection and re-reading of config file changes. * Improved signal handling, and a true daemon mode (Unix). * Every feature now controllable on a per-site or per-location basis, configuration more powerful and versatile over-all. * Many smaller new features added, limitations and bugs removed, and security holes fixed. ------------------------------------------------------------------------------- 2. Installation Privoxy is available both in convenient pre-compiled packages for a wide range of operating systems, and as raw source code. For most users, we recommend using the packages, which can be downloaded from our Privoxy Project Page. Note: On some platforms, the installer may remove previously installed versions, if found. (See below for your platform). In any case be sure to backup your old configuration if it is valuable to you. See the note to upgraders section below. ------------------------------------------------------------------------------- 2.1. Binary Packages How to install the binary packages depends on your operating system: ------------------------------------------------------------------------------- 2.1.1. Red Hat and Fedora RPMs RPMs can be installed with rpm -Uvh privoxy-3.0.6-1.rpm, and will use /etc/ privoxy for the location of configuration files. Note that on Red Hat, Privoxy will not be automatically started on system boot. You will need to enable that using chkconfig, ntsysv, or similar methods. If you have problems with failed dependencies, try rebuilding the SRC RPM: rpm --rebuild privoxy-3.0.6-1.src.rpm. This will use your locally installed libraries and RPM version. Also note that if you have a Junkbuster RPM installed on your system, you need to remove it first, because the packages conflict. Otherwise, RPM will try to remove Junkbuster automatically if found, before installing Privoxy. ------------------------------------------------------------------------------- 2.1.2. Debian DEBs can be installed with apt-get install privoxy, and will use /etc/privoxy for the location of configuration files. ------------------------------------------------------------------------------- 2.1.3. Windows Just double-click the installer, which will guide you through the installation process. You will find the configuration files in the same directory as you installed Privoxy in. Version 3.0.4 introduced full Windows service functionality. On Windows only, the Privoxy program has two new command line arguments to install and uninstall Privoxy as a service. Arguments: --install[:service_name] --uninstall[:service_name] After invoking Privoxy with --install, you will need to bring up the Windows service console to assign the user you want Privoxy to run under, and whether or not you want it to run whenever the system starts. You can start the Windows services console with the following command: services.msc. If you do not take the manual step of modifying Privoxy's service settings, it will not start. Note too that you will need to give Privoxy a user account that actually exists, or it will not be permitted to write to its log and configuration files. ------------------------------------------------------------------------------- 2.1.4. Solaris, NetBSD, FreeBSD, HP-UX Create a new directory, cd to it, then unzip and untar the archive. For the most part, you'll have to figure out where things go. ------------------------------------------------------------------------------- 2.1.5. OS/2 First, make sure that no previous installations of Junkbuster and / or Privoxy are left on your system. Check that no Junkbuster or Privoxy objects are in your startup folder. Then, just double-click the WarpIN self-installing archive, which will guide you through the installation process. A shadow of the Privoxy executable will be placed in your startup folder so it will start automatically whenever OS/2 starts. The directory you choose to install Privoxy into will contain all of the configuration files. ------------------------------------------------------------------------------- 2.1.6. Mac OSX Unzip the downloaded file (you can either double-click on the file from the finder, or from the desktop if you downloaded it there). Then, double-click on the package installer icon named Privoxy.pkg and follow the installation process. Privoxy will be installed in the folder /Library/Privoxy. It will start automatically whenever you start up. To prevent it from starting automatically, remove or rename the folder /Library/StartupItems/Privoxy. To start Privoxy by hand, double-click on StartPrivoxy.command in the /Library/ Privoxy folder. Or, type this command in the Terminal: /Library/Privoxy/StartPrivoxy.command You will be prompted for the administrator password. ------------------------------------------------------------------------------- 2.1.7. AmigaOS Copy and then unpack the lha archive to a suitable location. All necessary files will be installed into Privoxy directory, including all configuration and log files. To uninstall, just remove this directory. ------------------------------------------------------------------------------- 2.1.8. Gentoo Gentoo source packages (Ebuilds) for Privoxy are contained in the Gentoo Portage Tree (they are not on the download page, but there is a Gentoo section, where you can see when a new Privoxy Version is added to the Portage Tree). Before installing Privoxy under Gentoo just do first emerge rsync to get the latest changes from the Portage tree. With emerge privoxy you install the latest version. Configuration files are in /etc/privoxy, the documentation is in /usr/share/doc /privoxy-3.0.6 and the Log directory is in /var/log/privoxy. ------------------------------------------------------------------------------- 2.2. Building from Source The most convenient way to obtain the Privoxy sources is to download the source tarball from our project download page. If you like to live on the bleeding edge and are not afraid of using possibly unstable development versions, you can check out the up-to-the-minute version directly from the CVS repository. To build Privoxy from source, autoconf, GNU make (gmake), and, of course, a C compiler like gcc are required. When building from a source tarball, first unpack the source: tar xzvf privoxy-3.0.6-src* [.tgz or .tar.gz] cd privoxy-3.0.6 For retrieving the current CVS sources, you'll need a CVS client installed. Note that sources from CVS are typically development quality, and may not be stable, or well tested. To download CVS source, check the Sourceforge documentation, which might give commands like: cvs -d:pserver:anonymous@ijbswa.cvs.sourceforge.net:/cvsroot/ijbswa login cvs -z3 -d:pserver:anonymous@ijbswa.cvs.sourceforge.net:/cvsroot/ijbswa co current cd current This will create a directory named current/, which will contain the source tree. You can also check out any Privoxy "branch", just exchange the current name with the wanted branch name (Example: v_3_0_branch for the 3.0 cvs tree). It is also strongly recommended to not run Privoxy as root. You should configure/install/run Privoxy as an unprivileged user, preferably by creating a "privoxy" user and group just for this purpose. See your local documentation for the correct command line to do add new users and groups (something like adduser, but the command syntax may vary from platform to platform). /etc/passwd might then look like: privoxy:*:7777:7777:privoxy proxy:/no/home:/no/shell And then /etc/group, like: privoxy:*:7777: Some binary packages may do this for you. Then, to build from either unpacked tarball or CVS source: autoheader autoconf ./configure # (--help to see options) make # (the make from GNU, sometimes called gmake) su # Possibly required make -n install # (to see where all the files will go) make -s install # (to really install, -s to silence output) Using GNU make, you can have the first four steps automatically done for you by just typing: make in the freshly downloaded or unpacked source directory. To build an executable with security enhanced features so that users cannot easily bypass the proxy (e.g. "Go There Anyway"), or alter their own configurations, configure like this: ./configure --disable-toggle --disable-editor --disable-force Then build as above. WARNING: If installing as root, the install will fail unless a non-root user or group is specified, or a privoxy user and group already exist on the system. If a non-root user is specified, and no group, then the installation will try to also use a group of the same name as "user". If a group is specified (and no user), then the support files will be installed as writable by that group, and owned by the user running the installation. configure accepts --with-user and --with-group options for setting user and group ownership of the configuration files (which need to be writable by the daemon). The specified user must already exist. When starting Privoxy, it must be run as this same user to insure write access to configuration and log files! Alternately, you can specify user and group on the make command line, but be sure both already exist: make -s install USER=privoxy GROUP=privoxy The default installation path for make install is /usr/local. This may of course be customized with the various ./configure path options. If you are doing an install to anywhere besides /usr/local, be sure to set the appropriate paths with the correct configure options (./configure --help). Non-privileged users must of course have write access permissions to wherever the target installation is going. If you do install to /usr/local, the install will use sysconfdir=$prefix/etc/ privoxy by default. All other destinations, and the direct usage of --sysconfdir flag behave like normal, i.e. will not add the extra privoxy directory. This is for a safer install, as there may already exist another program that uses a file with the "config" name, and thus makes /usr/local/etc cleaner. If installing to /usr/local, the documentation will go by default to $prefix/ share/doc. But if this directory doesn't exist, it will then try $prefix/doc and install there before creating a new $prefix/share/doc just for Privoxy. Again, if the installs goes to /usr/local, the localstatedir (ie: var/) will default to /var instead of $prefix/var so the logs will go to /var/log/privoxy /, and the pid file will be created in /var/run/privoxy.pid. make install will attempt to set the correct values in config (main configuration file). You should check this to make sure all values are correct. If appropriate, an init script will be installed, but it is up to the user to determine how and where to start Privoxy. The init script should be checked for correct paths and values, if anything other than a default install is done. If install finds previous versions of local configuration files, most of these will not be overwritten, and the new ones will be installed with a "new" extension. default.action, default.filter, and standard.action will be overwritten. You will then need to manually update the other installed configuration files as needed. All template files will be overwritten. If you have customized, local templates, you should save these first, and in fact it is wise to always save any important configuration files "just in case". If a previous version of Privoxy is already running, you will have to restart it manually. For more detailed instructions on how to build Redhat RPMs, Windows self-extracting installers, building on platforms with special requirements etc, please consult the developer manual. ------------------------------------------------------------------------------- 2.3. Keeping your Installation Up-to-Date As user feedback comes in and development continues, we will make updated versions of both the main actions file (as a separate package) and the software itself (including the actions file) available for download. If you wish to receive an email notification whenever we release updates of Privoxy or the actions file, subscribe to our announce mailing list, ijbswa-announce@lists.sourceforge.net. In order not to lose your personal changes and adjustments when updating to the latest default.action file we strongly recommend that you use user.action and user.filter for your local customizations of Privoxy. See the Chapter on actions files for details. ------------------------------------------------------------------------------- 3. What's New in this Release There are many improvements and new features since Privoxy 3.0.3, the last stable release: * Multiple filter files can now be specified in config. This allows for locally defined filters that can be maintained separately from the filters as supplied by the developers, i.e. default.filter. * There are a number of new actions: + content-type-overwrite + crunch-client-header + crunch-if-none-match + crunch-server-header + filter-client-headers + filter-server-headers + force-text-mode + handle-as-empty-document + hide-accept-language + hide-content-disposition + hide-if-modified-since + inspect-jpegs + overwrite-last-modified + redirect + treat-forbidden-connects-like-blocks In addition, fast-redirects has been significantly improved with enhanced syntax. And hide-referrer has a new option, conditional block. * MS-Windows versions can now be installed and started as a Windows service. * config has two new options: enable-remote-http-toggle, and forwarded-connect-retries. And there is improved handling of the user-manual option, for placing documentation and help files on the local system. * There are six new filters. * Actions files problems and suggestions are now being directed to: http:// sourceforge.net/tracker/?group_id=11118&atid=460288. Please use this to report such configuration related problems as missed ads, sites that don't function properly due to one action or another, innocent images being blocked, etc. * In addition, there are numerous bug fixes and significant enhancements, including error pages should no longer be cached if the problem is fixed, much better DNS error handling, various logging improvements, and configuration updates for better ad blocking and junk elimination. ------------------------------------------------------------------------------- 3.1. Note to Upgraders A quick list of things to be aware of before upgrading from earlier versions of Privoxy: * Some installers may remove earlier versions completely, including configuration files. Save any important configuration files! * On the other hand, other installers may not overwrite any existing configuration files, thinking you will want to do that. You may want to manually check your saved files against the newer versions to see if the improvements have merit, or whether there are new options that you may want to consider. There are a number of new features, but most won't be available unless these features are incorporated into your configuration somehow. * See the full documentation on fast-redirects which has changed syntax, and will require adjustments to local configs, such as user.action. You must reference the new syntax: { +fast-redirects{check-decoded-url} } .example.com mybank.com .google. * The jarfile, cookie logger, is off by default now. * What constitutes a "default" configuration has changed, and you may want to review which actions are "on" by default. This is primarily a matter of emphasis, but some features you may have been used to, may now be "off" by default. There are also a number of new actions and filters you may want to consider, most of which are not fully incorporated into the default settings as yet (see above). * The default actions setting is now Cautious. Previous releases had a default setting of Medium. Experienced users may want to adjust this, as it is fairly conservative by Privoxy standards and past practices. See http:// config.privoxy.org/edit-actions-list?f=default. New users should try the default settings for a while before turning up the volume. * The default setting has filtering turned off, which subsequently means that compression is on. Remember that filtering does not work on compressed pages, so if you use, or want to use, filtering, you will need to force compression off. Example: { +filter{google} +prevent-compression } .google. Or if you use a number of filters, or filter many sites, you may just want to turn off compression for all sites in default.action (or user.action). * Also, session-cookies-only is off by default now. If you've liked this feature in the past, you may want to turn it back on in user.action now. * Some installers may not automatically start Privoxy after installation. ------------------------------------------------------------------------------- 4. Quickstart to Using Privoxy * Install Privoxy. See the Installation Section below for platform specific information. * Advanced users and those who want to offer Privoxy service to more than just their local machine should check the main config file, especially the security-relevant options. These are off by default. * Start Privoxy, if the installation program has not done this already (may vary according to platform). See the section Starting Privoxy. * Set your browser to use Privoxy as HTTP and HTTPS (SSL) proxy by setting the proxy configuration for address of 127.0.0.1 and port 8118. DO NOT activate proxying for FTP or any protocols besides HTTP and HTTPS (SSL)! It won't work! * Flush your browser's disk and memory caches, to remove any cached ad images. If using Privoxy to manage cookies, you should remove any currently stored cookies too. * A default installation should provide a reasonable starting point for most. There will undoubtedly be occasions where you will want to adjust the configuration, but that can be dealt with as the need arises. Little to no initial configuration is required in most cases. See the Configuration section for more configuration options, and how to customize your installation. You might also want to look at the next section for a quick introduction to how Privoxy blocks ads and banners. * If you experience ads that slip through, innocent images that are blocked, or otherwise feel the need to fine-tune Privoxy's behavior, take a look at the actions files. As a quick start, you might find the richly commented examples helpful. You can also view and edit the actions files through the web-based user interface. The Appendix "Troubleshooting: Anatomy of an Action" has hints on how to understand and debug actions that "misbehave". * For easy access to Privoxy's most important controls, drag the provided Bookmarklets into your browser's personal toolbar. * Please see the section Contacting the Developers on how to report bugs, problems with websites or to get help. * Now enjoy surfing with enhanced control, comfort and privacy! ------------------------------------------------------------------------------- 4.1. Quickstart to Ad Blocking Ad blocking is but one of Privoxy's array of features. Many of these features are for the technically minded advanced user. But, ad and banner blocking is surely common ground for everybody. This section will provide a quick summary of ad blocking so you can get up to speed quickly without having to read the more extensive information provided below, though this is highly recommended. First a bit of a warning ... blocking ads is much like blocking SPAM: the more aggressive you are about it, the more likely you are to block things that were not intended. And the more likely that some things may not work as intended. So there is a trade off here. If you want extreme ad free browsing, be prepared to deal with more "problem" sites, and to spend more time adjusting the configuration to solve these unintended consequences. In short, there is not an easy way to eliminate all ads. Either take the easy way and settle for most ads blocked with the default configuration, or jump in and tweak it for your personal surfing habits and preferences. Secondly, a brief explanation of Privoxy's "actions". "Actions" in this context, are the directives we use to tell Privoxy to perform some task relating to WWW transactions (i.e. web browsing). We tell Privoxy to take some "action". Each action has a unique name and function. While there are many potential actions in Privoxy's arsenal, only a few are used for ad blocking. Actions, and action configuration files, are explained in depth below. Actions are specified in Privoxy's configuration, followed by one or more URLs to which the action should apply. URLs can actually be URL type patterns that use wildcards so they can apply potentially to a range of similar URLs. The actions, together with the URL patterns are called a section. When you connect to a website, the full URL will either match one or more of the sections as defined in Privoxy's configuration, or not. If so, then Privoxy will perform the respective actions. If not, then nothing special happens. Furthermore, web pages may contain embedded, secondary URLs that your web browser will use to load additional components of the page, as it parses the original page's HTML content. An ad image for instance, is just an URL embedded in the page somewhere. The image itself may be on the same server, or a server somewhere else on the Internet. Complex web pages will have many such embedded URLs. Privoxy can deal with each URL individually, so, for instance, the main page text is not touched, but images from such-and-such server are blocked. The most important actions for basic ad blocking are: block, handle-as-image, handle-as-empty-document,and set-image-blocker: * block - this is perhaps the single most used action, and is particularly important for ad blocking. This action stops any contact between your browser and any URL patterns that match this action's configuration. It can be used for blocking ads, but also anything that is determined to be unwanted. By itself, it simply stops any communication with the remote server and sends Privoxy's own built-in BLOCKED page instead to let you now what has happened (with some exceptions, see below). * handle-as-image - tells Privoxy to treat this URL as an image. Privoxy's default configuration already does this for all common image types (e.g. GIF), but there are many situations where this is not so easy to determine. So we'll force it in these cases. This is particularly important for ad blocking, since only if we know that it's an image of some kind, can we replace it with an image of our choosing, instead of the Privoxy BLOCKED page (which would only result in a "broken image" icon). There are some limitations to this though. For instance, you can't just brute-force an image substitution for an entire HTML page in most situations. * handle-as-empty-document - sends an empty document instead of Privoxy's normal BLOCKED HTML page. This is useful for file types that are neither HTML nor images, such as blocking JavaScript files. * set-image-blocker - tells Privoxy what to display in place of an ad image that has hit a block rule. For this to come into play, the URL must match a block action somewhere in the configuration, and, it must also match an handle-as-image action. The configuration options on what to display instead of the ad are: pattern - a checkerboard pattern, so that an ad replacement is obvious. This is the default. blank - A very small empty GIF image is displayed. This is the so-called "invisible" configuration option. http:// - A redirect to any image anywhere of the user's choosing (advanced usage). The quickest way to adjust any of these settings is with your browser through the special Privoxy editor at http://config.privoxy.org/show-status (shortcut: http://p.p/show-status). This is an internal page, and does not require Internet access. Select the appropriate "actions" file, and click "Edit". It is best to put personal or local preferences in user.action since this is not meant to be overwritten during upgrades, and will over-ride the settings in other files. Here you can insert new "actions", and URLs for ad blocking or other purposes, and make other adjustments to the configuration. Privoxy will detect these changes automatically. A quick and simple step by step example: * Right click on the ad image to be blocked, then select "Copy Link Location" from the pop-up menu. * Set your browser to http://config.privoxy.org/show-status * Find user.action in the top section, and click on "Edit": Figure 1. Actions Files in Use [files-in-u] * You should have a section with only block listed under "Actions:". If not, click a "Insert new section below" button, and in the new section that just appeared, click the Edit button right under the word "Actions:". This will bring up a list of all actions. Find block near the top, and click in the "Enabled" column, then "Submit" just below the list. * Now, in the block actions section, click the "Add" button, and paste the URL the browser got from "Copy Link Location". Remove the http:// at the beginning of the URL. Then, click "Submit" (or "OK" if in a pop-up window). * Now go back to the original page, and press SHIFT-Reload (or flush all browser caches). The image should be gone now. This is a very crude and simple example. There might be good reasons to use a wildcard pattern match to include potentially similar images from the same site. For a more extensive explanation of "patterns", and the entire actions concept, see the Actions section. For advanced users who want to hand edit their config files, you might want to now go to the Actions Files Tutorial. The ideas explained therein also apply to the web-based editor. There are also various filters that can be used for ad blocking (filters are a special subset of actions). These fall into the "advanced" usage category, and are explained in depth in later sections. ------------------------------------------------------------------------------- 5. Starting Privoxy Before launching Privoxy for the first time, you will want to configure your browser(s) to use Privoxy as a HTTP and HTTPS (SSL) proxy. The default is 127.0.0.1 (or localhost) for the proxy address, and port 8118 (earlier versions used port 8000). This is the one configuration step that must be done! Please note that Privoxy can only proxy HTTP and HTTPS traffic. It will not work with FTP or other protocols. Figure 2. Proxy Configuration Showing Mozilla/Netscape HTTP and HTTPS (SSL) Settings [proxy_setu] With Firefox, this is typically set under: Tools -> Options -> General -> Connection Settings -> Manual Proxy Configuration Or optionally on some platforms: Edit -> Preferences -> General -> Connection Settings -> Manual Proxy Configuration With Netscape (and Mozilla), this can be set under: Edit -> Preferences -> Advanced -> Proxies -> HTTP Proxy For Internet Explorer v.5-6: Tools -> Internet Options -> Connections -> LAN Settings Then, check "Use Proxy" and fill in the appropriate info (Address: 127.0.0.1, Port: 8118). Include HTTPS (SSL), if you want HTTPS proxy support too (sometimes labeled "Secure"). Make sure any checkboxes like "Use the same proxy server for all protocols" is UNCHECKED. You want only HTTP and HTTPS (SSL)! Figure 3. Proxy Configuration Showing Internet Explorer HTTP and HTTPS (Secure) Settings [proxy2] After doing this, flush your browser's disk and memory caches to force a re-reading of all pages and to get rid of any ads that may be cached. Remove any cookies, if you want Privoxy to manage that. You are now ready to start enjoying the benefits of using Privoxy! Privoxy itself is typically started by specifying the main configuration file to be used on the command line. If no configuration file is specified on the command line, Privoxy will look for a file named config in the current directory. Except on Win32 where it will try config.txt. ------------------------------------------------------------------------------- 5.1. Red Hat and Fedora A default Red Hat installation may not start Privoxy upon boot. It will use the file /etc/privoxy/config as its main configuration file. # /etc/rc.d/init.d/privoxy start Or ... # service privoxy start ------------------------------------------------------------------------------- 5.2. Debian We use a script. Note that Debian typically starts Privoxy upon booting per default. It will use the file /etc/privoxy/config as its main configuration file. # /etc/init.d/privoxy start ------------------------------------------------------------------------------- 5.3. Windows Click on the Privoxy Icon to start Privoxy. If no configuration file is specified on the command line, Privoxy will look for a file named config.txt. Note that Windows will automatically start Privoxy when the system starts if you chose that option when installing. Privoxy can run with full Windows service functionality. On Windows only, the Privoxy program has two new command line arguments to install and uninstall Privoxy as a service. See the Windows Installation instructions for details. ------------------------------------------------------------------------------- 5.4. Solaris, NetBSD, FreeBSD, HP-UX and others Example Unix startup command: # /usr/sbin/privoxy /etc/privoxy/config ------------------------------------------------------------------------------- 5.5. OS/2 During installation, Privoxy is configured to start automatically when the system restarts. You can start it manually by double-clicking on the Privoxy icon in the Privoxy folder. ------------------------------------------------------------------------------- 5.6. Mac OSX During installation, Privoxy is configured to start automatically when the system restarts. To start Privoxy manually, double-click on the StartPrivoxy.command icon in the /Library/Privoxy folder. Or, type this command in the Terminal: /Library/Privoxy/StartPrivoxy.command You will be prompted for the administrator password. ------------------------------------------------------------------------------- 5.7. AmigaOS Start Privoxy (with RUN <>NIL:) in your startnet script (AmiTCP), in s: user-startup (RoadShow), as startup program in your startup script (Genesis), or as startup action (Miami and MiamiDx). Privoxy will automatically quit when you quit your TCP/IP stack (just ignore the harmless warning your TCP/IP stack may display that Privoxy is still running). ------------------------------------------------------------------------------- 5.8. Gentoo A script is again used. It will use the file /etc/privoxy/config as its main configuration file. /etc/init.d/privoxy start Note that Privoxy is not automatically started at boot time by default. You can change this with the rc-update command. rc-update add privoxy default ------------------------------------------------------------------------------- 5.9. Command Line Options Privoxy may be invoked with the following command-line options: * --version Print version info and exit. Unix only. * --help Print short usage info and exit. Unix only. * --no-daemon Don't become a daemon, i.e. don't fork and become process group leader, and don't detach from controlling tty. Unix only. * --pidfile FILE On startup, write the process ID to FILE. Delete the FILE on exit. Failure to create or delete the FILE is non-fatal. If no FILE option is given, no PID file will be used. Unix only. * --user USER[.GROUP] After (optionally) writing the PID file, assume the user ID of USER, and if included the GID of GROUP. Exit if the privileges are not sufficient to do so. Unix only. * --chroot Before changing to the user ID given in the --user option, chroot to that user's home directory, i.e. make the kernel pretend to the Privoxy process that the directory tree starts there. If set up carefully, this can limit the impact of possible vulnerabilities in Privoxy to the files contained in that hierarchy. Unix only. * configfile If no configfile is included on the command line, Privoxy will look for a file named "config" in the current directory (except on Win32 where it will look for "config.txt" instead). Specify full path to avoid confusion. If no config file is found, Privoxy will fail to start. On MS Windows only there are two additional command-line options to allow Privoxy to install and run as a service. See the Window Installation section for details. ------------------------------------------------------------------------------- 6. Privoxy Configuration All Privoxy configuration is stored in text files. These files can be edited with a text editor. Many important aspects of Privoxy can also be controlled easily with a web browser. ------------------------------------------------------------------------------- 6.1. Controlling Privoxy with Your Web Browser Privoxy's user interface can be reached through the special URL http:// config.privoxy.org/ (shortcut: http://p.p/), which is a built-in page and works without Internet access. You will see the following section: Privoxy Menu ? View & change the current configuration ? View the source code version numbers ? View the request headers. ? Look up which actions apply to a URL and why ? Toggle Privoxy on or off ? Documentation This should be self-explanatory. Note the first item leads to an editor for the actions files, which is where the ad, banner, cookie, and URL blocking magic is configured as well as other advanced features of Privoxy. This is an easy way to adjust various aspects of Privoxy configuration. The actions file, and other configuration files, are explained in detail below. "Toggle Privoxy On or Off" is handy for sites that might have problems with your current actions and filters. You can in fact use it as a test to see whether it is Privoxy causing the problem or not. Privoxy continues to run as a proxy in this case, but all manipulation is disabled, i.e. Privoxy acts like a normal forwarding proxy. There is even a toggle Bookmarklet offered, so that you can toggle Privoxy with one click from your browser. ------------------------------------------------------------------------------- 6.2. Configuration Files Overview For Unix, *BSD and Linux, all configuration files are located in /etc/privoxy/ by default. For MS Windows, OS/2, and AmigaOS these are all in the same directory as the Privoxy executable. The installed defaults provide a reasonable starting point, though some settings may be aggressive by some standards. For the time being, the principle configuration files are: * The main configuration file is named config on Linux, Unix, BSD, OS/2, and AmigaOS and config.txt on Windows. This is a required file. * default.action (the main actions file) is used to define which "actions" relating to banner-blocking, images, pop-ups, content modification, cookie handling etc should be applied by default. It also defines many exceptions (both positive and negative) from this default set of actions that enable Privoxy to selectively eliminate the junk, and only the junk, on as many websites as possible. Multiple actions files may be defined in config. These are processed in the order they are defined. Local customizations and locally preferred exceptions to the default policies as defined in default.action (which you will most probably want to define sooner or later) are probably best applied in user.action, where you can preserve them across upgrades. standard.action is only for Privoxy's internal use. There is also a web based editor that can be accessed from http:// config.privoxy.org/show-status (Shortcut: http://p.p/show-status) for the various actions files. * "Filter files" (the filter file) can be used to re-write the raw page content, including viewable text as well as embedded HTML and JavaScript, and whatever else lurks on any given web page. The filtering jobs are only pre-defined here; whether to apply them or not is up to the actions files. default.filter includes various filters made available for use by the developers. Some are much more intrusive than others, and all should be used with caution. You may define additional filter files in config as you can with actions files. We suggest user.filter for any locally defined filters or customizations. The syntax of all configuration files has remained the same throughout the 3.x series. There have been enhancements, but no changes that would preclude the use of any configuration file from one version to the next. (There is one exception: +fast-redirects which has enhanced syntax and will require updating any local configs from earlier versions.) All files use the "#" character to denote a comment (the rest of the line will be ignored) and understand line continuation through placing a backslash ("\") as the very last character in a line. If the # is preceded by a backslash, it looses its special function. Placing a # in front of an otherwise valid configuration line to prevent it from being interpreted is called "commenting out" that line. Blank lines are ignored. The actions files and filter files can use Perl style regular expressions for maximum flexibility. After making any changes, there is no need to restart Privoxy in order for the changes to take effect. Privoxy detects such changes automatically. Note, however, that it may take one or two additional requests for the change to take effect. When changing the listening address of Privoxy, these "wake up" requests must obviously be sent to the old listening address. ------------------------------------------------------------------------------- 7. The Main Configuration File Again, the main configuration file is named config on Linux/Unix/BSD and OS/2, and config.txt on Windows. Configuration lines consist of an initial keyword followed by a list of values, all separated by whitespace (any number of spaces or tabs). For example: confdir /etc/privoxy Assigns the value /etc/privoxy to the option confdir and thus indicates that the configuration directory is named "/etc/privoxy/". All options in the config file except for confdir and logdir are optional. Watch out in the below description for what happens if you leave them unset. The main config file controls all aspects of Privoxy's operation that are not location dependent (i.e. they apply universally, no matter where you may be surfing). ------------------------------------------------------------------------------- 7.1. Local Set-up Documentation If you intend to operate Privoxy for more users than just yourself, it might be a good idea to let them know how to reach you, what you block and why you do that, your policies, etc. ------------------------------------------------------------------------------- 7.1.1. user-manual Specifies: Location of the Privoxy User Manual. Type of value: A fully qualified URI Default value: Unset Effect if unset: http://www.privoxy.org/version/user-manual/ will be used, where version is the Privoxy version. Notes: The User Manual URI is the single best source of information on Privoxy, and is used for help links from some of the internal CGI pages. The manual itself is normally packaged with the binary distributions, so you probably want to set this to a locally installed copy. Examples: The best all purpose solution is simply to put the full local PATH to where the User Manual is located: user-manual /usr/share/doc/privoxy/user-manual The User Manual is then available to anyone with access to the proxy, by following the built-in URL: http://config.privoxy.org/user-manual/ (or the shortcut: http://p.p/user-manual/). If the documentation is not on the local system, it can be accessed from a remote server, as: user-manual http://example.com/privoxy/user-manual/ +-----------------------------------------------------------------+ | Warning | |-----------------------------------------------------------------| |If set, this option should be the first option in the config | |file, because it is used while the config file is being read on | |start-up. | +-----------------------------------------------------------------+ ------------------------------------------------------------------------------- 7.1.2. trust-info-url Specifies: A URL to be displayed in the error page that users will see if access to an untrusted page is denied. Type of value: URL Default value: Two example URL are provided Effect if unset: No links are displayed on the "untrusted" error page. Notes: The value of this option only matters if the experimental trust mechanism has been activated. (See trustfile above.) If you use the trust mechanism, it is a good idea to write up some on-line documentation about your trust policy and to specify the URL(s) here. Use multiple times for multiple URLs. The URL(s) should be added to the trustfile as well, so users don't end up locked out from the information on why they were locked out in the first place! ------------------------------------------------------------------------------- 7.1.3. admin-address Specifies: An email address to reach the proxy administrator. Type of value: Email address Default value: Unset Effect if unset: No email address is displayed on error pages and the CGI user interface. Notes: If both admin-address and proxy-info-url are unset, the whole "Local Privoxy Support" box on all generated pages will not be shown. ------------------------------------------------------------------------------- 7.1.4. proxy-info-url Specifies: A URL to documentation about the local Privoxy setup, configuration or policies. Type of value: URL Default value: Unset Effect if unset: No link to local documentation is displayed on error pages and the CGI user interface. Notes: If both admin-address and proxy-info-url are unset, the whole "Local Privoxy Support" box on all generated pages will not be shown. This URL shouldn't be blocked ;-) ------------------------------------------------------------------------------- 7.2. Configuration and Log File Locations Privoxy can (and normally does) use a number of other files for additional configuration, help and logging. This section of the configuration file tells Privoxy where to find those other files. The user running Privoxy, must have read permission for all configuration files, and write permission to any files that would be modified, such as log files and actions files. ------------------------------------------------------------------------------- 7.2.1. confdir Specifies: The directory where the other configuration files are located Type of value: Path name Default value: /etc/privoxy (Unix) or Privoxy installation dir (Windows) Effect if unset: Mandatory Notes: No trailing "/", please ------------------------------------------------------------------------------- 7.2.2. logdir Specifies: The directory where all logging takes place (i.e. where logfile and jarfile are located) Type of value: Path name Default value: /var/log/privoxy (Unix) or Privoxy installation dir (Windows) Effect if unset: Mandatory Notes: No trailing "/", please ------------------------------------------------------------------------------- 7.2.3. actionsfile Specifies: The actions file(s) to use Type of value: File name, relative to confdir, without the .action suffix Default values: standard # Internal purposes, no editing recommended default # Main actions file user # User customizations Effect if unset: No actions are taken at all. Simple neutral proxying. Notes: Multiple actionsfile lines are permitted, and are in fact recommended! The default values include standard.action, which is used for internal purposes and should be loaded, default.action, which is the "main" actions file maintained by the developers, and user.action, where you can make your personal additions. Actions files are where all the per site and per URL configuration is done for ad blocking, cookie management, privacy considerations, etc. There is no point in using Privoxy without at least one actions file. ------------------------------------------------------------------------------- 7.2.4. filterfile Specifies: The filter file(s) to use Type of value: File name, relative to confdir Default value: default.filter (Unix) or default.filter.txt (Windows) Effect if unset: No textual content filtering takes place, i.e. all +filter{name} actions in the actions files are turned neutral. Notes: Multiple filterfile lines are permitted. The filter files contain content modification rules that use regular expressions. These rules permit powerful changes on the content of Web pages, and optionally the headers as well, e.g., you could disable your favorite JavaScript annoyances, re-write the actual displayed text, or just have some fun playing buzzword bingo with web pages. The +filter{name} actions rely on the relevant filter (name) to be defined in a filter file! A pre-defined filter file called default.filter that contains a number of useful filters for common problems is included in the distribution. See the section on the filter action for a list. It is recommended to place any locally adapted filters into a separate file, such as user.filter. ------------------------------------------------------------------------------- 7.2.5. logfile Specifies: The log file to use Type of value: File name, relative to logdir Default value: logfile (Unix) or privoxy.log (Windows) Effect if unset: No log file is used, all log messages go to the console (STDERR). Notes: The logfile is where all logging and error messages are written. The level of detail and number of messages are set with the debug option (see below). The logfile can be useful for tracking down a problem with Privoxy (e.g., it's not blocking an ad you think it should block) but in most cases you probably will never look at it. Your logfile will grow indefinitely, and you will probably want to periodically remove it. On Unix systems, you can do this with a cron job (see "man cron"). For Red Hat, a logrotate script has been included. On SuSE Linux systems, you can place a line like "/var/log/privoxy.* +1024k 644 nobody.nogroup" in /etc/logfiles, with the effect that cron.daily will automatically archive, gzip, and empty the log, when it exceeds 1M size. Any log files must be writable by whatever user Privoxy is being run as (default on UNIX, user id is "privoxy"). ------------------------------------------------------------------------------- 7.2.6. jarfile Specifies: The file to store intercepted cookies in Type of value: File name, relative to logdir Default value: Unset (commented out). When activated: jarfile (Unix) or privoxy.jar (Windows) Effect if unset: Intercepted cookies are not stored in a dedicated log file. Notes: The jarfile may grow to ridiculous sizes over time. If debug 8 (show header parsing) is enabled, cookies are written to the logfile with the rest of the headers. ------------------------------------------------------------------------------- 7.2.7. trustfile Specifies: The name of the trust file to use Type of value: File name, relative to confdir Default value: Unset (commented out). When activated: trust (Unix) or trust.txt (Windows) Effect if unset: The entire trust mechanism is disabled. Notes: The trust mechanism is an experimental feature for building white-lists and should be used with care. It is NOT recommended for the casual user. If you specify a trust file, Privoxy will only allow access to sites that are specified in the trustfile. Sites can be listed in one of two ways: Prepending a ~ character limits access to this site only (and any sub-paths within this site), e.g. ~www.example.com allows access to ~www.example.com/ features/news.html, etc. Or, you can designate sites as trusted referrers, by prepending the name with a + character. The effect is that access to untrusted sites will be granted -- but only if a link from this trusted referrer was used to get there. The link target will then be added to the "trustfile" so that future, direct accesses will be granted. Sites added via this mechanism do not become trusted referrers themselves (i.e. they are added with a ~ designation). There is a limit of 512 such entries, after which new entries will not be made. If you use the + operator in the trust file, it may grow considerably over time. It is recommended that Privoxy be compiled with the --disable-force, --disable-toggle and --disable-editor options, if this feature is to be used. Possible applications include limiting Internet access for children. ------------------------------------------------------------------------------- 7.3. Debugging These options are mainly useful when tracing a problem. Note that you might also want to invoke Privoxy with the --no-daemon command line option when debugging. ------------------------------------------------------------------------------- 7.3.1. debug Specifies: Key values that determine what information gets logged to the logfile. Type of value: Integer values Default value: 12289 (i.e.: URLs plus informational and warning messages) Effect if unset: Nothing gets logged. Notes: The available debug levels are: debug 1 # show each GET/POST/CONNECT request debug 2 # show each connection status debug 4 # show I/O status debug 8 # show header parsing debug 16 # log all data into the logfile debug 32 # debug force feature debug 64 # debug regular expression filter debug 128 # debug fast redirects debug 256 # debug GIF de-animation debug 512 # Common Log Format debug 1024 # debug kill pop-ups debug 2048 # CGI user interface debug 4096 # Startup banner and warnings. debug 8192 # Non-fatal errors To select multiple debug levels, you can either add them or use multiple debug lines. A debug level of 1 is informative because it will show you each request as it happens. 1, 4096 and 8192 are highly recommended so that you will notice when things go wrong. The other levels are probably only of interest if you are hunting down a specific problem. They can produce a hell of an output (especially 16). The reporting of fatal errors (i.e. ones which crash Privoxy) is always on and cannot be disabled. If you want to use CLF (Common Log Format), you should set "debug 512" ONLY and not enable anything else. ------------------------------------------------------------------------------- 7.3.2. single-threaded Specifies: Whether to run only one server thread Type of value: None Default value: Unset Effect if unset: Multi-threaded (or, where unavailable: forked) operation, i.e. the ability to serve multiple requests simultaneously. Notes: This option is only there for debug purposes and you should never need to use it. It will drastically reduce performance. ------------------------------------------------------------------------------- 7.4. Access Control and Security This section of the config file controls the security-relevant aspects of Privoxy's configuration. ------------------------------------------------------------------------------- 7.4.1. listen-address Specifies: The IP address and TCP port on which Privoxy will listen for client requests. Type of value: [IP-Address]:Port Default value: 127.0.0.1:8118 Effect if unset: Bind to 127.0.0.1 (localhost), port 8118. This is suitable and recommended for home users who run Privoxy on the same machine as their browser. Notes: You will need to configure your browser(s) to this proxy address and port. If you already have another service running on port 8118, or if you want to serve requests from other machines (e.g. on your local network) as well, you will need to override the default. If you leave out the IP address, Privoxy will bind to all interfaces (addresses) on your machine and may become reachable from the Internet. In that case, consider using access control lists (ACL's, see below), and/or a firewall. If you open Privoxy to untrusted users, you will also want to turn off the enable-edit-actions and enable-remote-toggle options! Example: Suppose you are running Privoxy on a machine which has the address 192.168.0.1 on your local private network (192.168.0.0) and has another outside connection with a different address. You want it to serve requests from inside only: listen-address 192.168.0.1:8118 ------------------------------------------------------------------------------- 7.4.2. toggle Specifies: Initial state of "toggle" status Type of value: 1 or 0 Default value: 1 Effect if unset: Act as if toggled on Notes: If set to 0, Privoxy will start in "toggled off" mode, i.e. behave like a normal, content-neutral proxy where all ad blocking, filtering, etc are disabled. See enable-remote-toggle below. This is not really useful anymore, since toggling is much easier via the web interface than via editing the conf file. The windows version will only display the toggle icon in the system tray if this option is present. ------------------------------------------------------------------------------- 7.4.3. enable-remote-toggle Specifies: Whether or not the web-based toggle feature may be used Type of value: 0 or 1 Default value: 1 Effect if unset: The web-based toggle feature is disabled. Notes: When toggled off, Privoxy acts like a normal, content-neutral proxy, i.e. it acts as if none of the actions applied to any URL. For the time being, access to the toggle feature can not be controlled separately by "ACLs" or HTTP authentication, so that everybody who can access Privoxy (see "ACLs" and listen-address above) can toggle it for all users. So this option is not recommended for multi-user environments with untrusted users. Note that you must have compiled Privoxy with support for this feature, otherwise this option has no effect. ------------------------------------------------------------------------------- 7.4.4. enable-remote-http-toggle Specifies: Whether or not Privoxy recognizes special HTTP headers to change its behaviour. Type of value: 0 or 1 Default value: 1 Effect if unset: Privoxy ignores special HTTP headers. Notes: When toggled on, the client can change Privoxy's behaviour by setting special HTTP headers. Currently the only supported special header is "X-Filter: No", to disable filtering for the ongoing request, even if it is enabled in one of the action files. If you are using Privoxy in a multi-user environment or with untrustworthy clients and want to enforce filtering, you will have to disable this option, otherwise you can ignore it. ------------------------------------------------------------------------------- 7.4.5. enable-edit-actions Specifies: Whether or not the web-based actions file editor may be used Type of value: 0 or 1 Default value: 1 Effect if unset: The web-based actions file editor is disabled. Notes: For the time being, access to the editor can not be controlled separately by "ACLs" or HTTP authentication, so that everybody who can access Privoxy (see "ACLs" and listen-address above) can modify its configuration for all users. So this option is not recommended for multi-user environments with untrusted users. Note that you must have compiled Privoxy with support for this feature, otherwise this option has no effect. ------------------------------------------------------------------------------- 7.4.6. ACLs: permit-access and deny-access Specifies: Who can access what. Type of value: src_addr[/src_masklen] [dst_addr[/dst_masklen]] Where src_addr and dst_addr are IP addresses in dotted decimal notation or valid DNS names, and src_masklen and dst_masklen are subnet masks in CIDR notation, i.e. integer values from 2 to 30 representing the length (in bits) of the network address. The masks and the whole destination part are optional. Default value: Unset Effect if unset: Don't restrict access further than implied by listen-address Notes: Access controls are included at the request of ISPs and systems administrators, and are not usually needed by individual users. For a typical home user, it will normally suffice to ensure that Privoxy only listens on the localhost (127.0.0.1) or internal (home) network address by means of the listen-address option. Please see the warnings in the FAQ that this proxy is not intended to be a substitute for a firewall or to encourage anyone to defer addressing basic security weaknesses. Multiple ACL lines are OK. If any ACLs are specified, then the Privoxy talks only to IP addresses that match at least one permit-access line and don't match any subsequent deny-access line. In other words, the last match wins, with the default being deny-access. If Privoxy is using a forwarder (see forward below) for a particular destination URL, the dst_addr that is examined is the address of the forwarder and NOT the address of the ultimate target. This is necessary because it may be impossible for the local Privoxy to determine the IP address of the ultimate target (that's often what gateways are used for). You should prefer using IP addresses over DNS names, because the address lookups take time. All DNS names must resolve! You can not use domain patterns like "*.org" or partial domain names. If a DNS name resolves to multiple IP addresses, only the first one is used. Denying access to particular sites by ACL may have undesired side effects if the site in question is hosted on a machine which also hosts other sites. Examples: Explicitly define the default behavior if no ACL and listen-address are set: "localhost" is OK. The absence of a dst_addr implies that all destination addresses are OK: permit-access localhost Allow any host on the same class C subnet as www.privoxy.org access to nothing but www.example.com: permit-access www.privoxy.org/24 www.example.com/32 Allow access from any host on the 26-bit subnet 192.168.45.64 to anywhere, with the exception that 192.168.45.73 may not access www.dirty-stuff.example.com: permit-access 192.168.45.64/26 deny-access 192.168.45.73 www.dirty-stuff.example.com ------------------------------------------------------------------------------- 7.4.7. buffer-limit Specifies: Maximum size of the buffer for content filtering. Type of value: Size in Kbytes Default value: 4096 Effect if unset: Use a 4MB (4096 KB) limit. Notes: For content filtering, i.e. the +filter and +deanimate-gif actions, it is necessary that Privoxy buffers the entire document body. This can be potentially dangerous, since a server could just keep sending data indefinitely and wait for your RAM to exhaust -- with nasty consequences. Hence this option. When a document buffer size reaches the buffer-limit, it is flushed to the client unfiltered and no further attempt to filter the rest of the document is made. Remember that there may be multiple threads running, which might require up to buffer-limit Kbytes each, unless you have enabled "single-threaded" above. ------------------------------------------------------------------------------- 7.5. Forwarding This feature allows routing of HTTP requests through a chain of multiple proxies. It can be used to better protect privacy and confidentiality when accessing specific domains by routing requests to those domains through an anonymous public proxy. Or to use a caching proxy to speed up browsing. Or chaining to a parent proxy may be necessary because the machine that Privoxy runs on has no direct Internet access. Also specified here are SOCKS proxies. Privoxy supports the SOCKS 4 and SOCKS 4A protocols. ------------------------------------------------------------------------------- 7.5.1. forward Specifies: To which parent HTTP proxy specific requests should be routed. Type of value: target_pattern http_parent[:port] where target_pattern is a URL pattern that specifies to which requests (i.e. URLs) this forward rule shall apply. Use / to denote "all URLs". http_parent[:port] is the DNS name or IP address of the parent HTTP proxy through which the requests should be forwarded, optionally followed by its listening port (default: 8080). Use a single dot (.) to denote "no forwarding". Default value: Unset Effect if unset: Don't use parent HTTP proxies. Notes: If http_parent is ".", then requests are not forwarded to another HTTP proxy but are made directly to the web servers. Multiple lines are OK, they are checked in sequence, and the last match wins. Examples: Everything goes to an example anonymizing proxy, except SSL on port 443 (which it doesn't handle): forward / anon-proxy.example.org:8080 forward :443 . Everything goes to our example ISP's caching proxy, except for requests to that ISP's sites: forward / caching-proxy.example-isp.net:8000 forward .example-isp.net . ------------------------------------------------------------------------------- 7.5.2. forward-socks4 and forward-socks4a Specifies: Through which SOCKS proxy (and to which parent HTTP proxy) specific requests should be routed. Type of value: target_pattern socks_proxy[:port] http_parent[:port] where target_pattern is a URL pattern that specifies to which requests (i.e. URLs) this forward rule shall apply. Use / to denote "all URLs". http_parent and socks_proxy are IP addresses in dotted decimal notation or valid DNS names (http_parent may be "." to denote "no HTTP forwarding"), and the optional port parameters are TCP ports, i.e. integer values from 1 to 64535 Default value: Unset Effect if unset: Don't use SOCKS proxies. Notes: Multiple lines are OK, they are checked in sequence, and the last match wins. The difference between forward-socks4 and forward-socks4a is that in the SOCKS 4A protocol, the DNS resolution of the target hostname happens on the SOCKS server, while in SOCKS 4 it happens locally. If http_parent is ".", then requests are not forwarded to another HTTP proxy but are made (HTTP-wise) directly to the web servers, albeit through a SOCKS proxy. Examples: From the company example.com, direct connections are made to all "internal" domains, but everything outbound goes through their ISP's proxy by way of example.com's corporate SOCKS 4A gateway to the Internet. forward-socks4a / socks-gw.example.com:1080 www-cache.example-isp.net:8080 forward .example.com . A rule that uses a SOCKS 4 gateway for all destinations but no HTTP parent looks like this: forward-socks4 / socks-gw.example.com:1080 . To chain Privoxy and Tor, both running on the same system, you should use the rule: forward-socks4 / 127.0.0.1:9050 . The public Tor network can't be used to reach your local network, therefore it's a good idea to make some exceptions: forward 192.168.*.*/ . forward 10.*.*.*/ . forward 127.*.*.*/ . Unencrypted connections to systems in these address ranges will be as (un) secure as the local network is, but the alternative is that you can't reach the network at all. If you also want to be able to reach servers in your local network by using their names, you will need additional exceptions that look like this: forward localhost/ . ------------------------------------------------------------------------------- 7.5.3. Advanced Forwarding Examples If you have links to multiple ISPs that provide various special content only to their subscribers, you can configure multiple Privoxies which have connections to the respective ISPs to act as forwarders to each other, so that your users can see the internal content of all ISPs. Assume that host-a has a PPP connection to isp-a.net. And host-b has a PPP connection to isp-b.net. Both run Privoxy. Their forwarding configuration can look like this: host-a: forward / . forward .isp-b.net host-b:8118 host-b: forward / . forward .isp-a.net host-a:8118 Now, your users can set their browser's proxy to use either host-a or host-b and be able to browse the internal content of both isp-a and isp-b. If you intend to chain Privoxy and squid locally, then chain as browser -> squid -> privoxy is the recommended way. Assuming that Privoxy and squid run on the same box, your squid configuration could then look like this: # Define Privoxy as parent proxy (without ICP) cache_peer 127.0.0.1 parent 8118 7 no-query # Define ACL for protocol FTP acl ftp proto FTP # Do not forward FTP requests to Privoxy always_direct allow ftp # Forward all the rest to Privoxy never_direct allow all You would then need to change your browser's proxy settings to squid's address and port. Squid normally uses port 3128. If unsure consult http_port in squid.conf. You could just as well decide to only forward requests for Windows executables through a virus-scanning parent proxy, say, on antivir.example.com, port 8010: forward / . forward /.*\.(exe|com|dll|zip)$ antivir.example.com:8010 ------------------------------------------------------------------------------- 7.5.4. forwarded-connect-retries Specifies: How often Privoxy retries if a forwarded connection request fails. Type of value: Number of retries. Default value: 0 Effect if unset: Forwarded connections are treated like direct connections and no retry attempts are made. Notes: forwarded-connect-retries is mainly interesting for socks4a connections, where Privoxy can't detect why the connections failed. The connection might have failed because of a DNS timeout in which case a retry makes sense, but it might also have failed because the server doesn't exist or isn't reachable. In this case the retry will just delay the appearance of Privoxy's error message. Only use this option, if you are getting many forwarding related error messages, that go away when you try again manually. Start with a small value and check Privoxy's logfile from time to time, to see how many retries are usually needed. Examples: forwarded-connect-retries 1 ------------------------------------------------------------------------------- 7.6. Windows GUI Options Privoxy has a number of options specific to the Windows GUI interface: If "activity-animation" is set to 1, the Privoxy icon will animate when "Privoxy" is active. To turn off, set to 0. activity-animation 1 If "log-messages" is set to 1, Privoxy will log messages to the console window: log-messages 1 If "log-buffer-size" is set to 1, the size of the log buffer, i.e. the amount of memory used for the log messages displayed in the console window, will be limited to "log-max-lines" (see below). Warning: Setting this to 0 will result in the buffer to grow infinitely and eat up all your memory! log-buffer-size 1 log-max-lines is the maximum number of lines held in the log buffer. See above. log-max-lines 200 If "log-highlight-messages" is set to 1, Privoxy will highlight portions of the log messages with a bold-faced font: log-highlight-messages 1 The font used in the console window: log-font-name Comic Sans MS Font size used in the console window: log-font-size 8 "show-on-task-bar" controls whether or not Privoxy will appear as a button on the Task bar when minimized: show-on-task-bar 0 If "close-button-minimizes" is set to 1, the Windows close button will minimize Privoxy instead of closing the program (close with the exit option on the File menu). close-button-minimizes 1 The "hide-console" option is specific to the MS-Win console version of Privoxy. If this option is used, Privoxy will disconnect from and hide the command console. #hide-console ------------------------------------------------------------------------------- 8. Actions Files The actions files are used to define what actions Privoxy takes for which URLs, and thus determines how ad images, cookies and various other aspects of HTTP content and transactions are handled, and on which sites (or even parts thereof). There are a number of such actions, with a wide range of functionality. Each action does something a little different. These actions give us a veritable arsenal of tools with which to exert our control, preferences and independence. Actions can be combined so that their effects are aggregated when applied against a given set of URLs. There are three action files included with Privoxy with differing purposes: * default.action - is the primary action file that sets the initial values for all actions. It is intended to provide a base level of functionality for Privoxy's array of features. So it is a set of broad rules that should work reasonably well as-is for most users. This is the file that the developers are keeping updated, and making available to users. The user's preferences as set in standard.action, e.g. either Cautious (the default), Medium, or Advanced (see below). * user.action - is intended to be for local site preferences and exceptions. As an example, if your ISP or your bank has specific requirements, and need special handling, this kind of thing should go here. This file will not be upgraded. * standard.action - is used only by the web based editor at http:// config.privoxy.org/edit-actions-list?f=default, to set various pre-defined sets of rules for the default actions section in default.action. Edit Set to Cautious Set to Medium Set to Advanced These have increasing levels of aggressiveness and have no influence on your browsing unless you select them explicitly in the editor. A default installation should be pre-set to Cautious (versions prior to 3.0.5 were set to Medium). New users should try this for a while before adjusting the settings to more aggressive levels. The more aggressive the settings, then the more likelihood there is of problems such as sites not working as they should. The Edit button allows you to turn each action on/off individually for fine-tuning. The Cautious button changes the actions list to low/safe settings which will activate ad blocking and a minimal set of Privoxy's features, and subsequently there will be less of a chance for accidental problems. The Medium button sets the list to a medium level of other features and a low level set of privacy features. The Advanced button sets the list to a high level of ad blocking and medium level of privacy. See the chart below. The latter three buttons over-ride any changes via with the Edit button. More fine-tuning can be done in the lower sections of this internal page. It is not recommend to edit the standard.action file itself. The default profiles, and their associated actions, as pre-defined in standard.action are: Table 1. Default Configurations +-------------------------------------------------------------------------+ |Feature |Cautious |Medium |Advanced | |------------------+-----------------+------------------+-----------------| |Ad-blocking |medium |high |high | |Aggressiveness | | | | |------------------+-----------------+------------------+-----------------| |Ad-filtering by |no |yes |yes | |size | | | | |------------------+-----------------+------------------+-----------------| |Ad-filtering by |no |no |yes | |link | | | | |------------------+-----------------+------------------+-----------------| |Pop-up killing |blocks only |blocks only |blocks only | |------------------+-----------------+------------------+-----------------| |Privacy Features |low |medium |medium/high | |------------------+-----------------+------------------+-----------------| |Cookie handling |none |session-only |kill | |------------------+-----------------+------------------+-----------------| |Referer forging |no |yes |yes | |------------------+-----------------+------------------+-----------------| |GIF de-animation |no |yes |yes | |------------------+-----------------+------------------+-----------------| |Fast redirects |no |no |yes | |------------------+-----------------+------------------+-----------------| |HTML taming |no |no |yes | |------------------+-----------------+------------------+-----------------| |JavaScript taming |no |no |yes | |------------------+-----------------+------------------+-----------------| |Web-bug killing |no |yes |yes | |------------------+-----------------+------------------+-----------------| |Image tag |no |no |yes | |reordering | | | | +-------------------------------------------------------------------------+ The list of actions files to be used are defined in the main configuration file, and are processed in the order they are defined (e.g. default.action is typically process before user.action). The content of these can all be viewed and edited from http://config.privoxy.org/show-status. The over-riding principle when applying actions, is that the last action that matches a given URL, wins. The broadest, most general rules go first (defined in default.action), followed by any exceptions (typically also in default.action), which are then followed lastly by any local preferences (typically in user.action). Generally, user.action has the last word. An actions file typically has multiple sections. If you want to use "aliases" in an actions file, you have to place the (optional) alias section at the top of that file. Then comes the default set of rules which will apply universally to all sites and pages (be very careful with using such a universal set in user.action or any other actions file after default.action, because it will override the result from consulting any previous file). And then below that, exceptions to the defined universal policies. You can regard user.action as an appendix to default.action, with the advantage that is a separate file, which makes preserving your personal settings across Privoxy upgrades easier. Actions can be used to block anything you want, including ads, banners, or just some obnoxious URL that you would rather not see. Cookies can be accepted or rejected, or accepted only during the current browser session (i.e. not written to disk), content can be modified, JavaScripts tamed, user-tracking fooled, and much more. See below for a complete list of actions. ------------------------------------------------------------------------------- 8.1. Finding the Right Mix Note that some actions, like cookie suppression or script disabling, may render some sites unusable that rely on these techniques to work properly. Finding the right mix of actions is not always easy and certainly a matter of personal taste. And, things can always change, requiring refinements in the configuration. In general, it can be said that the more "aggressive" your default settings (in the top section of the actions file) are, the more exceptions for "trusted" sites you will have to make later. If, for example, you want to crunch all cookies per default, you'll have to make exceptions from that rule for sites that you regularly use and that require cookies for actually useful purposes, like maybe your bank, favorite shop, or newspaper. We have tried to provide you with reasonable rules to start from in the distribution actions files. But there is no general rule of thumb on these things. There just are too many variables, and sites are constantly changing. Sooner or later you will want to change the rules (and read this chapter again :). ------------------------------------------------------------------------------- 8.2. How to Edit The easiest way to edit the actions files is with a browser by using our browser-based editor, which can be reached from http://config.privoxy.org/ show-status. The editor allows both fine-grained control over every single feature on a per-URL basis, and easy choosing from wholesale sets of defaults like "Cautious", "Medium" or "Advanced". Warning: the "Advanced" setting is more aggressive, and will be more likely to cause problems for some sites. Experienced users only! If you prefer plain text editing to GUIs, you can of course also directly edit the the actions files with your favorite text editor. Look at default.action which is richly commented with many good examples. ------------------------------------------------------------------------------- 8.3. How Actions are Applied to URLs Actions files are divided into sections. There are special sections, like the " alias" sections which will be discussed later. For now let's concentrate on regular sections: They have a heading line (often split up to multiple lines for readability) which consist of a list of actions, separated by whitespace and enclosed in curly braces. Below that, there is a list of URL patterns, each on a separate line. To determine which actions apply to a request, the URL of the request is compared to all patterns in each "action file" file. Every time it matches, the list of applicable actions for the URL is incrementally updated, using the heading of the section in which the pattern is located. If multiple matches for the same URL set the same action differently, the last match wins. If not, the effects are aggregated. E.g. a URL might match a regular section with a heading line of { +handle-as-image }, then later another one with just { +block }, resulting in both actions to apply. And there may well be cases where you will want to combine actions together. Such a section then might look like: { +handle-as-image +block } # Block these as if they were images. Send no block page. banners.example.com media.example.com/.*banners .example.com/images/ads/ You can trace this process for any given URL by visiting http:// config.privoxy.org/show-url-info. Examples and more detail on this is provided in the Appendix, Troubleshooting: Anatomy of an Action section. ------------------------------------------------------------------------------- 8.4. Patterns As mentioned, Privoxy uses "patterns" to determine what actions might apply to which sites and pages your browser attempts to access. These "patterns" use wild card type pattern matching to achieve a high degree of flexibility. This allows one expression to be expanded and potentially match against many similar patterns. Generally, a Privoxy pattern has the form /, where both the and are optional. (This is why the special / pattern matches all URLs). Note that the protocol portion of the URL pattern (e.g. http://) should not be included in the pattern. This is assumed already! The pattern matching syntax is different for the domain and path parts of the URL. The domain part uses a simple globbing type matching technique, while the path part uses a more flexible "Regular Expressions (PCRE)" based syntax. www.example.com/ is a domain-only pattern and will match any request to www.example.com, regardless of which document on that server is requested. So ALL pages in this domain would be covered by the scope of this action. Note that a simple example.com is different and would NOT match. www.example.com means exactly the same. For domain-only patterns, the trailing / may be omitted. www.example.com/index.html matches only the single document /index.html on www.example.com. /index.html matches the document /index.html, regardless of the domain, i.e. on any web server anywhere. index.html matches nothing, since it would be interpreted as a domain name and there is no top-level domain called .html. So its a mistake. ------------------------------------------------------------------------------- 8.4.1. The Domain Pattern The matching of the domain part offers some flexible options: if the domain starts or ends with a dot, it becomes unanchored at that end. For example: .example.com matches any domain that ENDS in .example.com www. matches any domain that STARTS with www. .example. matches any domain that CONTAINS .example.. And, by the way, also included would be any files or documents that exist within that domain since no path limitations are specified. (Correctly speaking: It matches any FQDN that contains example as a domain.) This might be www.example.com, news.example.de, or www.example.net/cgi/testing.pl for instance. All these cases are matched. Additionally, there are wild-cards that you can use in the domain names themselves. These work similarly to shell globbing type wild-cards: "*" represents zero or more arbitrary characters (this is equivalent to the "Regular Expression" based syntax of ".*"), "?" represents any single character (this is equivalent to the regular expression syntax of a simple "."), and you can define "character classes" in square brackets which is similar to the same regular expression technique. All of this can be freely mixed: ad*.example.com matches "adserver.example.com", "ads.example.com", etc but not "sfads.example.com" *ad*.example.com matches all of the above, and then some. .?pix.com matches www.ipix.com, pictures.epix.com, a.b.c.d.e.upix.com etc. www[1-9a-ez].example.c* matches www1.example.com, www4.example.cc, wwwd.example.cy, wwwz.example.com etc., but not wwww.example.com. While flexible, this is not the sophistication of full regular expression based syntax. ------------------------------------------------------------------------------- 8.4.2. The Path Pattern Privoxy uses Perl compatible (PCRE) "Regular Expression" based syntax (through the PCRE library) for matching the path portion (after the slash), and is thus more flexible. There is an Appendix with a brief quick-start into regular expressions, and full (very technical) documentation on PCRE regex syntax is available on-line at http://www.pcre.org/man.txt. You might also find the Perl man page on regular expressions (man perlre) useful, which is available on-line at http:// perldoc.perl.org/perlre.html. Note that the path pattern is automatically left-anchored at the "/", i.e. it matches as if it would start with a "^" (regular expression speak for the beginning of a line). Please also note that matching in the path is CASE INSENSITIVE by default, but you can switch to case sensitive at any point in the pattern by using the "(? -i)" switch: www.example.com/(?-i)PaTtErN.* will match only documents whose path starts with PaTtErN in exactly this capitalization. .example.com/.* Is equivalent to just ".example.com", since any documents within that domain are matched with or without the ".*" regular expression. This is redundant .example.com/.*/index.html Will match any page in the domain of "example.com" that is named "index.html", and that is part of some path. For example, it matches "www.example.com/testing/index.html" but NOT "www.example.com/index.html" because the regular expression called for at least two "/'s", thus the path requirement. It also would match "www.example.com/testing/index_html", because of the special meta-character ".". .example.com/(.*/)?index\.html This regular expression is conditional so it will match any page named "index.html" regardless of path which in this case can have one or more "/ 's". And this one must contain exactly ".html" (but does not have to end with that!). .example.com/(.*/)(ads|banners?|junk) This regular expression will match any path of "example.com" that contains any of the words "ads", "banner", "banners" (because of the "?") or "junk". The path does not have to end in these words, just contain them. .example.com/(.*/)(ads|banners?|junk)/.*\.(jpe?g|gif|png)$ This is very much the same as above, except now it must end in either ".jpg", ".jpeg", ".gif" or ".png". So this one is limited to common image formats. There are many, many good examples to be found in default.action, and more tutorials below in Appendix on regular expressions. ------------------------------------------------------------------------------- 8.5. Actions All actions are disabled by default, until they are explicitly enabled somewhere in an actions file. Actions are turned on if preceded with a "+", and turned off if preceded with a "-". So a +action means "do that action", e.g. +block means "please block URLs that match the following patterns", and -block means "don't block URLs that match the following patterns, even if +block previously applied." Again, actions are invoked by placing them on a line, enclosed in curly braces and separated by whitespace, like in {+some-action -some-other-action {some-parameter}}, followed by a list of URL patterns, one per line, to which they apply. Together, the actions line and the following pattern lines make up a section of the actions file. Actions fall into three categories: * Boolean, i.e the action can only be "enabled" or "disabled". Syntax: +name # enable action name -name # disable action name Example: +block * Parameterized, where some value is required in order to enable this type of action. Syntax: +name{param} # enable action and set parameter to param, # overwriting parameter from previous match if necessary -name # disable action. The parameter can be omitted Note that if the URL matches multiple positive forms of a parameterized action, the last match wins, i.e. the params from earlier matches are simply ignored. Example: +hide-user-agent{ Mozilla 1.0 } * Multi-value. These look exactly like parameterized actions, but they behave differently: If the action applies multiple times to the same URL, but with different parameters, all the parameters from all matches are remembered. This is used for actions that can be executed for the same request repeatedly, like adding multiple headers, or filtering through multiple filters. Syntax: +name{param} # enable action and add param to the list of parameters -name{param} # remove the parameter param from the list of parameters # If it was the last one left, disable the action. -name # disable this action completely and remove all parameters from the list Examples: +add-header{X-Fun-Header: Some text} and +filter{html-annoyances} If nothing is specified in any actions file, no "actions" are taken. So in this case Privoxy would just be a normal, non-blocking, non-anonymizing proxy. You must specifically enable the privacy and blocking features you need (although the provided default actions files will give a good starting point). Later defined actions always over-ride earlier ones. So exceptions to any rules you make, should come in the latter part of the file (or in a file that is processed later when using multiple actions files such as user.action). For multi-valued actions, the actions are applied in the order they are specified. Actions files are processed in the order they are defined in config (the default installation has three actions files). It also quite possible for any given URL to match more than one "pattern" (because of wildcards and regular expressions), and thus to trigger more than one set of actions! Last match wins. The list of valid Privoxy actions are: ------------------------------------------------------------------------------- 8.5.1. add-header Typical use: Confuse log analysis, custom applications Effect: Sends a user defined HTTP header to the web server. Type: Multi-value. Parameter: Any string value is possible. Validity of the defined HTTP headers is not checked. It is recommended that you use the "X-" prefix for custom headers. Notes: This action may be specified multiple times, in order to define multiple headers. This is rarely needed for the typical user. If you don't know what "HTTP headers" are, you definitely don't need to worry about this one. Example usage: +add-header{X-User-Tracking: sucks} ------------------------------------------------------------------------------- 8.5.2. block Typical use: Block ads or other unwanted content Effect: Requests for URLs to which this action applies are blocked, i.e. the requests are trapped by Privoxy and the requested URL is never retrieved, but is answered locally with a substitute page or image, as determined by the handle-as-image, set-image-blocker, and handle-as-empty-document actions. Type: Boolean. Parameter: N/A Notes: Privoxy sends a special "BLOCKED" page for requests to blocked pages. This page contains links to find out why the request was blocked, and a click-through to the blocked content (the latter only if compiled with the force feature enabled). The "BLOCKED" page adapts to the available screen space -- it displays full-blown if space allows, or miniaturized and text-only if loaded into a small frame or window. If you are using Privoxy right now, you can take a look at the "BLOCKED" page. A very important exception occurs if both block and handle-as-image, apply to the same request: it will then be replaced by an image. If set-image-blocker (see below) also applies, the type of image will be determined by its parameter, if not, the standard checkerboard pattern is sent. It is important to understand this process, in order to understand how Privoxy deals with ads and other unwanted content. Blocking is a core feature, and one upon which various other features depend. The filter action can perform a very similar task, by "blocking" banner images and other content through rewriting the relevant URLs in the document's HTML source, so they don't get requested in the first place. Note that this is a totally different technique, and it's easy to confuse the two. Example usage (section): {+block} # Block and replace with "blocked" page .nasty-stuff.example.com {+block +handle-as-image} # Block and replace with image .ad.doubleclick.net .ads.r.us/banners/ {+block +handle-as-empty-document} # Block and then ignore adserver.exampleclick.net/.*\.js$ ------------------------------------------------------------------------------- 8.5.3. content-type-overwrite Typical use: Stop useless download menus from popping up, or change the browser's rendering mode Effect: Replaces the "Content-Type:" HTTP server header. Type: Parameterized. Parameter: Any string. Notes: The "Content-Type:" HTTP server header is used by the browser to decide what to do with the document. The value of this header can cause the browser to open a download menu instead of displaying the document by itself, even if the document's format is supported by the browser. The declared content type can also affect which rendering mode the browser chooses. If XHTML is delivered as "text/html", many browsers treat it as yet another broken HTML document. If it is send as "application/xml", browsers with XHTML support will only display it, if the syntax is correct. If you see a web site that proudly uses XHTML buttons, but sets "Content-Type: text/html", you can use Privoxy to overwrite it with "application/xml" and validate the web master's claim inside your XHTML-supporting browser. If the syntax is incorrect, the browser will complain loudly. You can also go the opposite direction: if your browser prints error messages instead of rendering a document falsely declared as XHTML, you can overwrite the content type with "text/html" and have it rendered as broken HTML document. By default content-type-overwrite only replaces "Content-Type:" headers that look like some kind of text. If you want to overwrite it unconditionally, you have to combine it with force-text-mode. This limitation exists for a reason, think twice before circumventing it. Most of the time it's easier to enable filter-server-headers and replace this action with a custom regular expression. It allows you to activate it for every document of a certain site and it will still only replace the content types you aimed at. Of course you can apply content-type-overwrite to a whole site and then make URL based exceptions, but it's a lot more work to get the same precision. Example usage (sections): # Check if www.example.net/ really uses valid XHTML { +content-type-overwrite{application/xml} } www.example.net/ # but leave the content type unmodified if the URL looks like a style sheet {-content-type-overwrite} www.example.net/*.\.css$ www.example.net/*.style ------------------------------------------------------------------------------- 8.5.4. crunch-client-header Typical use: Remove a client header Privoxy has no dedicated action for. Effect: Deletes every header sent by the client that contains the string the user supplied as parameter. Type: Parameterized. Parameter: Any string. Notes: This action allows you to block client headers for which no dedicated Privoxy action exists. Privoxy will remove every client header that contains the string you supplied as parameter. Regular expressions are not supported and you can't use this action to block different headers in the same request, unless they contain the same string. crunch-client-header is only meant for quick tests. If you have to block several different headers, or only want to modify parts of them, you should enable filter-client-headers and create your own filter. +-----------------------------------------------------------------+ | Warning | |-----------------------------------------------------------------| |Don't block any header without understanding the consequences. | +-----------------------------------------------------------------+ Example usage (section): # Block the non-existent "Privacy-Violation:" client header { +crunch-client-header{Privacy-Violation:} } / ------------------------------------------------------------------------------- 8.5.5. crunch-if-none-match Typical use: Prevent yet another way to track the user's steps between sessions. Effect: Deletes the "If-None-Match:" HTTP client header. Type: Boolean. Parameter: N/A Notes: Removing the "If-None-Match:" HTTP client header is useful for filter testing, where you want to force a real reload instead of getting status code "304" which would cause the browser to use a cached copy of the page. It is also useful to make sure the header isn't used as a cookie replacement. Blocking the "If-None-Match:" header shouldn't cause any caching problems, as long as the "If-Modified-Since:" header isn't blocked as well. It is recommended to use this action together with hide-if-modified-since and overwrite-last-modified. Example usage (section): # Let the browser revalidate cached documents without being tracked across sessions { +hide-if-modified-since{-60} \ +overwrite-last-modified{randomize} \ +crunch-if-none-match} / ------------------------------------------------------------------------------- 8.5.6. crunch-incoming-cookies Typical use: Prevent the web server from setting any cookies on your system Effect: Deletes any "Set-Cookie:" HTTP headers from server replies. Type: Boolean. Parameter: N/A Notes: This action is only concerned with incoming cookies. For outgoing cookies, use crunch-outgoing-cookies. Use both to disable cookies completely. It makes no sense at all to use this action in conjunction with the session-cookies-only action, since it would prevent the session cookies from being set. See also filter-content-cookies. Example usage: +crunch-incoming-cookies ------------------------------------------------------------------------------- 8.5.7. crunch-server-header Typical use: Remove a server header Privoxy has no dedicated action for. Effect: Deletes every header sent by the server that contains the string the user supplied as parameter. Type: Parameterized. Parameter: Any string. Notes: This action allows you to block server headers for which no dedicated Privoxy action exists. Privoxy will remove every server header that contains the string you supplied as parameter. Regular expressions are not supported and you can't use this action to block different headers in the same request, unless they contain the same string. crunch-server-header is only meant for quick tests. If you have to block several different headers, or only want to modify parts of them, you should enable filter-server-headers and create your own filter. +-----------------------------------------------------------------+ | Warning | |-----------------------------------------------------------------| |Don't block any header without understanding the consequences. | +-----------------------------------------------------------------+ Example usage (section): # Crunch server headers that try to prevent caching { +crunch-server-header{no-cache} } / ------------------------------------------------------------------------------- 8.5.8. crunch-outgoing-cookies Typical use: Prevent the web server from reading any cookies from your system Effect: Deletes any "Cookie:" HTTP headers from client requests. Type: Boolean. Parameter: N/A Notes: This action is only concerned with outgoing cookies. For incoming cookies, use crunch-incoming-cookies. Use both to disable cookies completely. It makes no sense at all to use this action in conjunction with the session-cookies-only action, since it would prevent the session cookies from being read. Example usage: +crunch-outgoing-cookies ------------------------------------------------------------------------------- 8.5.9. deanimate-gifs Typical use: Stop those annoying, distracting animated GIF images. Effect: De-animate GIF animations, i.e. reduce them to their first or last image. Type: Parameterized. Parameter: "last" or "first" Notes: This will also shrink the images considerably (in bytes, not pixels!). If the option "first" is given, the first frame of the animation is used as the replacement. If "last" is given, the last frame of the animation is used instead, which probably makes more sense for most banner animations, but also has the risk of not showing the entire last frame (if it is only a delta to an earlier frame). You can safely use this action with patterns that will also match non-GIF objects, because no attempt will be made at anything that doesn't look like a GIF. Example usage: +deanimate-gifs{last} ------------------------------------------------------------------------------- 8.5.10. downgrade-http-version Typical use: Work around (very rare) problems with HTTP/1.1 Effect: Downgrades HTTP/1.1 client requests and server replies to HTTP/1.0. Type: Boolean. Parameter: N/A Notes: This is a left-over from the time when Privoxy didn't support important HTTP/1.1 features well. It is left here for the unlikely case that you experience HTTP/1.1 related problems with some server out there. Not all (optional) HTTP/1.1 features are supported yet, so there is a chance you might need this action. Example usage (section): {+downgrade-http-version} problem-host.example.com ------------------------------------------------------------------------------- 8.5.11. fast-redirects Typical use: Fool some click-tracking scripts and speed up indirect links. Effect: Detects redirection URLs and redirects the browser without contacting the redirection server first. Type: Parameterized. Parameter: + "simple-check" to just search for the string "http://" to detect redirection URLs. + "check-decoded-url" to decode URLs (if necessary) before searching for redirection URLs. Notes: Many sites, like yahoo.com, don't just link to other sites. Instead, they will link to some script on their own servers, giving the destination as a parameter, which will then redirect you to the final target. URLs resulting from this scheme typically look like: "http://www.example.org/ click-tracker.cgi?target=http%3a//www.example.net/". Sometimes, there are even multiple consecutive redirects encoded in the URL. These redirections via scripts make your web browsing more traceable, since the server from which you follow such a link can see where you go to. Apart from that, valuable bandwidth and time is wasted, while your browser asks the server for one redirect after the other. Plus, it feeds the advertisers. This feature is currently not very smart and is scheduled for improvement. If it is enabled by default, you will have to create some exceptions to this action. It can lead to failures in several ways: Not every URLs with other URLs as parameters is evil. Some sites offer a real service that requires this information to work. For example a validation service needs to know, which document to validate. fast-redirects assumes that every URL parameter that looks like another URL is a redirection target, and will always redirect to the last one. Most of the time the assumption is correct, but if it isn't, the user gets redirected anyway. Another failure occurs if the URL contains other parameters after the URL parameter. The URL: "http://www.example.org/?redirect=http%3a// www.example.net/&foo=bar". contains the redirection URL "http:// www.example.net/", followed by another parameter. fast-redirects doesn't know that and will cause a redirect to "http://www.example.net/&foo=bar". Depending on the target server configuration, the parameter will be silently ignored or lead to a "page not found" error. It is possible to fix these redirected requests with filter-client-headers but it requires a little effort. To detect a redirection URL, fast-redirects only looks for the string "http://", either in plain text (invalid but often used) or encoded as "http%3a//". Some sites use their own URL encoding scheme, encrypt the address of the target server or replace it with a database id. In theses cases fast-redirects is fooled and the request reaches the redirection server where it probably gets logged. Example usage: { +fast-redirects{simple-check} } .example.com { +fast-redirects{check-decoded-url} } another.example.com/testing ------------------------------------------------------------------------------- 8.5.12. filter Typical use: Get rid of HTML and JavaScript annoyances, banner advertisements (by size), do fun text replacements, add personalized effects, etc. Effect: All files of text-based type, most notably HTML and JavaScript, to which this action applies, can be filtered on-the-fly through the specified regular expression based substitutions. (Note: as of version 3.0.3 plain text documents are exempted from filtering, because web servers often use the text/plain MIME type for all files whose type they don't know.) By default, filtering works only on the raw document content itself (that which can be seen with View Source), not the headers. Type: Parameterized. Parameter: The name of a filter, as defined in the filter file. Filters can be defined in one or more files as defined by the filterfile option in the config file . default.filter is the collection of filters supplied by the developers. Locally defined filters should go in their own file, such as user.filter. When used in its negative form, and without parameters, all filtering is completely disabled. Notes: For your convenience, there are a number of pre-defined filters available in the distribution filter file that you can use. See the examples below for a list. Filtering requires buffering the page content, which may appear to slow down page rendering since nothing is displayed until all content has passed the filters. (It does not really take longer, but seems that way since the page is not incrementally displayed.) This effect will be more noticeable on slower connections. "Rolling your own" filters requires a knowledge of "Regular Expressions" and "HTML". This is very powerful feature, and potentially very intrusive. Filters should be used with caution, and where an equivalent "action" is not available. The amount of data that can be filtered is limited to the buffer-limit option in the main config file. The default is 4096 KB (4 Megs). Once this limit is exceeded, the buffered data, and all pending data, is passed through unfiltered. Inappropriate MIME types, such as zipped files, are not filtered at all. (Again, only text-based types except plain text). Encrypted SSL data (from HTTPS servers) cannot be filtered either, since this would violate the integrity of the secure transaction. In some situations it might be necessary to protect certain text, like source code, from filtering by defining appropriate -filter exceptions. At this time, Privoxy cannot uncompress compressed documents. If you want filtering to work on all documents, even those that would normally be sent compressed, you must use the prevent-compression action in conjunction with filter. Filtering can achieve some of the same effects as the block action, i.e. it can be used to block ads and banners. But the mechanism works quite differently. One effective use, is to block ad banners based on their size (see below), since many of these seem to be somewhat standardized. Feedback with suggestions for new or improved filters is particularly welcome! The below list has only the names and a one-line description of each predefined filter. There are more verbose explanations of what these filters do in the filter file chapter. Example usage (with filters from the distribution default.filter file). See the Predefined Filters section for more explanation on each: +filter{js-annoyances} # Get rid of particularly annoying JavaScript abuse +filter{js-events} # Kill all JS event bindings (Radically destructive! Only for extra nasty sites) +filter{html-annoyances} # Get rid of particularly annoying HTML abuse +filter{content-cookies} # Kill cookies that come in the HTML or JS content +filter{refresh-tags} # Kill automatic refresh tags (for dial-on-demand setups) +filter{unsolicited-popups} # Disable only unsolicited pop-up windows. Useful if your browser lacks this ability. +filter{all-popups} # Kill all popups in JavaScript and HTML. Useful if your browser lacks this ability. +filter{img-reorder} # Reorder attributes in tags to make the banners-by-* filters more effective +filter{banners-by-size} # Kill banners by size +filter{banners-by-link} # Kill banners by their links to known clicktrackers +filter{webbugs} # Squish WebBugs (1x1 invisible GIFs used for user tracking) +filter{tiny-textforms} # Extend those tiny textareas up to 40x80 and kill the hard wrap +filter{jumping-windows} # Prevent windows from resizing and moving themselves +filter{frameset-borders} # Give frames a border and make them resizeable +filter{demoronizer} # Fix MS's non-standard use of standard charsets +filter{shockwave-flash} # Kill embedded Shockwave Flash objects +filter{quicktime-kioskmode} # Make Quicktime movies savable +filter{fun} # Text replacements for subversive browsing fun! +filter{crude-parental} # Crude parental filtering (demo only) +filter{ie-exploits} # Disable some known Internet Explorer bug exploits +filter{site-specifics} # Custom filters for specific site related problems +filter{google} # Removes text ads and other Google specific improvements +filter{yahoo} # Removes text ads and other Yahoo specific improvements +filter{msn} # Removes text ads and other MSN specific improvements +filter{blogspot} # Cleans up Blogspot blogs +filter{html-to-xml} # Header filter to change the Content-Type from html to xml +filter{xml-to-html} # Header filter to change the Content-Type from xml to html +filter{no-ping} # Removes non-standard ping attributes from anchor and area tags +filter{hide-tor-exit-notation} # Header filter to remove the Tor exit node notation in Host and Referer headers ------------------------------------------------------------------------------- 8.5.13. filter-client-headers Typical use: To apply filtering to the client's (browser's) headers Effect: By default, Privoxy's filters only apply to the document content itself. This will extend those filters to include the client's headers as well. Type: Boolean. Parameter: N/A Notes: Regular expressions can be used to filter headers as well. Check your filters closely before activating this action, as it can easily lead to broken requests. These filters are applied to each header on its own, not to them all at once. This makes it easier to diagnose problems, but on the downside you can't write filters that only change header x if header y's value is z. The filters are used after the other header actions have finished and can use their output as input. Whenever possible one should specify ^, $, the whole header name and the colon, to make sure the filter doesn't cause havoc to other headers or the page itself. For example if you want to transform Galeon User-Agents to Firefox User-Agents you shouldn't use: s@Galeon/\d\.\d\.\d @@ but: s@^(User-Agent:.*) Galeon/\d\.\d\.\d (Firefox/\d\.\d\.\d\.\d)$@$1 $2@ Example usage (section): {+filter-client-headers +filter{test_filter}} problem-host.example.com ------------------------------------------------------------------------------- 8.5.14. filter-server-headers Typical use: To apply filtering to the server's headers Effect: By default, Privoxy's filters only apply to the document content itself. This will extend those filters to include the server's headers as well. Type: Boolean. Parameter: N/A Notes: Similar to filter-client-headers, but works on the server instead. To filter both server and client, use both. As with filter-client-headers, check your filters before activating this action, as it can easily lead to broken requests. These filters are applied to each header on its own, not to them all at once. This makes it easier to diagnose problems, but on the downside you can't write filters that only change header x if header y's value is z. The filters are used after the other header actions have finished and can use their output as input. Remember too, whenever possible one should specify ^, $, the whole header name and the colon, to make sure the filter doesn't cause havoc to other headers or the page itself. See above for example. Example usage (section): {+filter-server-headers +filter{test_filter}} problem-host.example.com ------------------------------------------------------------------------------- 8.5.15. force-text-mode Typical use: Force Privoxy to treat a document as if it was in some kind of text format. Effect: Declares a document as text, even if the "Content-Type:" isn't detected as such. Type: Boolean. Parameter: N/A Notes: As explained above, Privoxy tries to only filter files that are in some kind of text format. The same restrictions apply to content-type-overwrite. force-text-mode declares a document as text, without looking at the "Content-Type:" first. +-----------------------------------------------------------------+ | Warning | |-----------------------------------------------------------------| |Think twice before activating this action. Filtering binary data | |with regular expressions can cause file damage. | +-----------------------------------------------------------------+ Example usage: +force-text-mode ------------------------------------------------------------------------------- 8.5.16. handle-as-empty-document Typical use: Mark URLs that should be replaced by empty documents if they get blocked Effect: This action alone doesn't do anything noticeable. It just marks URLs. If the block action also applies, the presence or absence of this mark decides whether an HTML "BLOCKED" page, or an empty document will be sent to the client as a substitute for the blocked content. The empty document isn't literally empty, but actually contains a single space. Type: Boolean. Parameter: N/A Notes: Some browsers complain about syntax errors if JavaScript documents are blocked with Privoxy's default HTML page; this option can be used to silence them. And of course this action can also be used to eliminate the Privoxy BLOCKED message in frames. The content type for the empty document can be specified with content-type-overwrite{}, but usually this isn't necessary. Example usage: # Block all documents on example.org that end with ".js", # but send an empty document instead of the usual HTML message. {+block +handle-as-empty-document} example.org/.*\.js$ ------------------------------------------------------------------------------- 8.5.17. handle-as-image Typical use: Mark URLs as belonging to images (so they'll be replaced by images if they do get blocked, rather than HTML pages) Effect: This action alone doesn't do anything noticeable. It just marks URLs as images. If the block action also applies, the presence or absence of this mark decides whether an HTML "blocked" page, or a replacement image (as determined by the set-image-blocker action) will be sent to the client as a substitute for the blocked content. Type: Boolean. Parameter: N/A Notes: The below generic example section is actually part of default.action. It marks all URLs with well-known image file name extensions as images and should be left intact. Users will probably only want to use the handle-as-image action in conjunction with block, to block sources of banners, whose URLs don't reflect the file type, like in the second example section. Note that you cannot treat HTML pages as images in most cases. For instance, (in-line) ad frames require an HTML page to be sent, or they won't display properly. Forcing handle-as-image in this situation will not replace the ad frame with an image, but lead to error messages. Example usage (sections): # Generic image extensions: # {+handle-as-image} /.*\.(gif|jpg|jpeg|png|bmp|ico)$ # These don't look like images, but they're banners and should be # blocked as images: # {+block +handle-as-image} some.nasty-banner-server.com/junk.cgi?output=trash # Banner source! Who cares if they also have non-image content? ad.doubleclick.net ------------------------------------------------------------------------------- 8.5.18. hide-accept-language Typical use: Pretend to use different language settings. Effect: Deletes or replaces the "Accept-Language:" HTTP header in client requests. Type: Parameterized. Parameter: Keyword: "block", or any user defined value. Notes: Faking the browser's language settings can be useful to make a foreign User-Agent set with hide-user-agent more believable. However some sites with content in different languages check the "Accept-Language:" to decide which one to take by default. Sometimes it isn't possible to later switch to another language without changing the "Accept-Language:" header first. Therefore it's a good idea to either only change the "Accept-Language:" header to languages you understand, or to languages that aren't wide spread. Before setting the "Accept-Language:" header to a rare language, you should consider that it helps to make your requests unique and thus easier to trace. If you don't plan to change this header frequently, you should stick to a common language. Example usage (section): # Pretend to use Canadian language settings. {+hide-accept-language{en-ca} \ +hide-user-agent{Mozilla/5.0 (X11; U; OpenBSD i386; en-CA; rv:1.8.0.4) Gecko/20060628 Firefox/1.5.0.4} \ } / ------------------------------------------------------------------------------- 8.5.19. hide-content-disposition Typical use: Prevent download menus for content you prefer to view inside the browser. Effect: Deletes or replaces the "Content-Disposition:" HTTP header set by some servers. Type: Parameterized. Parameter: Keyword: "block", or any user defined value. Notes: Some servers set the "Content-Disposition:" HTTP header for documents they assume you want to save locally before viewing them. The "Content-Disposition:" header contains the file name the browser is supposed to use by default. In most browsers that understand this header, it makes it impossible to just view the document, without downloading it first, even if it's just a simple text file or an image. Removing the "Content-Disposition:" header helps to prevent this annoyance, but some browsers additionally check the "Content-Type:" header, before they decide if they can display a document without saving it first. In these cases, you have to change this header as well, before the browser stops displaying download menus. It is also possible to change the server's file name suggestion to another one, but in most cases it isn't worth the time to set it up. Example usage: # Disarm the download link in Sourceforge's patch tracker { -filter \ +content-type-overwrite{text/plain}\ +hide-content-disposition{block} } .sourceforge.net/tracker/download.php ------------------------------------------------------------------------------- 8.5.20. hide-if-modified-since Typical use: Prevent yet another way to track the user's steps between sessions. Effect: Deletes the "If-Modified-Since:" HTTP client header or modifies its value. Type: Parameterized. Parameter: Keyword: "block", or a user defined value that specifies a range of hours. Notes: Removing this header is useful for filter testing, where you want to force a real reload instead of getting status code "304", which would cause the browser to use a cached copy of the page. Instead of removing the header, hide-if-modified-since can also add or subtract a random amount of time to/from the header's value. You specify a range of minutes where the random factor should be chosen from and Privoxy does the rest. A negative value means subtracting, a positive value adding. Randomizing the value of the "If-Modified-Since:" makes sure it isn't used as a cookie replacement, but you will run into caching problems if the random range is too high. It is a good idea to only use a small negative value and let overwrite-last-modified handle the greater changes. It is also recommended to use this action together with crunch-if-none-match. Example usage (section): # Let the browser revalidate without being tracked across sessions { +hide-if-modified-since{-60} \ +overwrite-last-modified{randomize} \ +crunch-if-none-match} / ------------------------------------------------------------------------------- 8.5.21. hide-forwarded-for-headers Typical use: Improve privacy by hiding the true source of the request Effect: Deletes any existing "X-Forwarded-for:" HTTP header from client requests, and prevents adding a new one. Type: Boolean. Parameter: N/A Notes: It is fairly safe to leave this on. This action is scheduled for improvement: It should be able to generate forged "X-Forwarded-for:" headers using random IP addresses from a specified network, to make successive requests from the same client look like requests from a pool of different users sharing the same proxy. Example usage: +hide-forwarded-for-headers ------------------------------------------------------------------------------- 8.5.22. hide-from-header Typical use: Keep your (old and ill) browser from telling web servers your email address Effect: Deletes any existing "From:" HTTP header, or replaces it with the specified string. Type: Parameterized. Parameter: Keyword: "block", or any user defined value. Notes: The keyword "block" will completely remove the header (not to be confused with the block action). Alternately, you can specify any value you prefer to be sent to the web server. If you do, it is a matter of fairness not to use any address that is actually used by a real person. This action is rarely needed, as modern web browsers don't send "From:" headers anymore. Example usage: +hide-from-header{block} or +hide-from-header{spam-me-senseless@sittingduck.example.com} ------------------------------------------------------------------------------- 8.5.23. hide-referrer Typical use: Conceal which link you followed to get to a particular site Effect: Deletes the "Referer:" (sic) HTTP header from the client request, or replaces it with a forged one. Type: Parameterized. Parameter: + "conditional-block" to delete the header completely if the host has changed. + "block" to delete the header unconditionally. + "forge" to pretend to be coming from the homepage of the server we are talking to. + Any other string to set a user defined referrer. Notes: conditional-block is the only parameter, that isn't easily detected in the server's log file. If it blocks the referrer, the request will look like the visitor used a bookmark or typed in the address directly. Leaving the referrer unmodified for requests on the same host allows the server owner to see the visitor's "click path", but in most cases she could also get that information by comparing other parts of the log file: for example the User-Agent if it isn't a very common one, or the user's IP address if it doesn't change between different requests. Always blocking the referrer, or using a custom one, can lead to failures on servers that check the referrer before they answer any requests, in an attempt to prevent their valuable content from being embedded or linked to elsewhere. Both conditional-block and forge will work with referrer checks, as long as content and valid referring page are on the same host. Most of the time that's the case. hide-referer is an alternate spelling of hide-referrer and the two can be can be freely substituted with each other. ("referrer" is the correct English spelling, however the HTTP specification has a bug - it requires it to be spelled as "referer".) Example usage: +hide-referrer{forge} or +hide-referrer{http://www.yahoo.com/} ------------------------------------------------------------------------------- 8.5.24. hide-user-agent Typical use: Conceal your type of browser and client operating system Effect: Replaces the value of the "User-Agent:" HTTP header in client requests with the specified value. Type: Parameterized. Parameter: Any user-defined string. Notes: +-----------------------------------------------------------------+ | Warning | |-----------------------------------------------------------------| |This can lead to problems on web sites that depend on looking at | |this header in order to customize their content for different | |browsers (which, by the way, is NOT the right thing to do: good | |web sites work browser-independently). | +-----------------------------------------------------------------+ Using this action in multi-user setups or wherever different types of browsers will access the same Privoxy is not recommended. In single-user, single-browser setups, you might use it to delete your OS version information from the headers, because it is an invitation to exploit known bugs for your OS. It is also occasionally useful to forge this in order to access sites that won't let you in otherwise (though there may be a good reason in some cases). Example of this: some MSN sites will not let Mozilla enter, yet forging to a Netscape 6.1 user-agent works just fine. (Must be just a silly MS goof, I'm sure :-). This action is scheduled for improvement. Example usage: +hide-user-agent{Netscape 6.1 (X11; I; Linux 2.4.18 i686)} ------------------------------------------------------------------------------- 8.5.25. inspect-jpegs Typical use: To protect against the MS buffer over-run in JPEG processing Effect: Protect against a known exploit Type: Boolean. Parameter: N/A Notes: See Microsoft Security Bulletin MS04-028. JPEG images are one of the most common image types found across the Internet. The exploit as described can allow execution of code on the target system, giving an attacker access to the system in question by merely planting an altered JPEG image, which would have no obvious indications of what lurks inside. This action prevents unwanted intrusion. Example usage: +inspect-jpegs ------------------------------------------------------------------------------- 8.5.26. kill-popups Typical use: Eliminate those annoying pop-up windows (deprecated) Effect: While loading the document, replace JavaScript code that opens pop-up windows with (syntactically neutral) dummy code on the fly. Type: Boolean. Parameter: N/A Notes: This action is basically a built-in, hardwired special-purpose filter action, but there are important differences: For kill-popups, the document need not be buffered, so it can be incrementally rendered while downloading. But kill-popups doesn't catch as many pop-ups as filter {all-popups} does and is not as smart as filter{unsolicited-popups} is. Think of it as a fast and efficient replacement for a filter that you can use if you don't want any filtering at all. Note that it doesn't make sense to combine it with any filter action, since as soon as one filter applies, the whole document needs to be buffered anyway, which destroys the advantage of the kill-popups action over its filter equivalent. Killing all pop-ups unconditionally is problematic. Many shops and banks rely on pop-ups to display forms, shopping carts etc, and the filter {unsolicited-popups} does a better job of catching only the unwanted ones. If the only kind of pop-ups that you want to kill are exit consoles (those really nasty windows that appear when you close an other one), you might want to use filter{js-annoyances} instead. This action is most appropriate for browsers that don't have any controls for unwanted pop-ups. Not recommended for general usage. Example usage: +kill-popups ------------------------------------------------------------------------------- 8.5.27. limit-connect Typical use: Prevent abuse of Privoxy as a TCP proxy relay or disable SSL for untrusted sites Effect: Specifies to which ports HTTP CONNECT requests are allowable. Type: Parameterized. Parameter: A comma-separated list of ports or port ranges (the latter using dashes, with the minimum defaulting to 0 and the maximum to 65K). Notes: By default, i.e. if no limit-connect action applies, Privoxy only allows HTTP CONNECT requests to port 443 (the standard, secure HTTPS port). Use limit-connect if more fine-grained control is desired for some or all destinations. The CONNECT methods exists in HTTP to allow access to secure websites ("https://" URLs) through proxies. It works very simply: the proxy connects to the server on the specified port, and then short-circuits its connections to the client and to the remote server. This can be a big security hole, since CONNECT-enabled proxies can be abused as TCP relays very easily. Privoxy relays HTTPS traffic without seeing the decoded content. Websites can leverage this limitation to circumvent Privoxy's filters. By specifying an invalid port range you can disable HTTPS entirely. If you plan to disable SSL by default, consider enabling treat-forbidden-connects-like-blocks as well, to be able to quickly create exceptions. Example usages: +limit-connect{443} # This is the default and need not be specified. +limit-connect{80,443} # Ports 80 and 443 are OK. +limit-connect{-3, 7, 20-100, 500-} # Ports less than 3, 7, 20 to 100 and above 500 are OK. +limit-connect{-} # All ports are OK +limit-connect{,} # No HTTPS/SSL traffic is allowed ------------------------------------------------------------------------------- 8.5.28. prevent-compression Typical use: Ensure that servers send the content uncompressed, so it can be passed through filters. Effect: Removes the Accept-Encoding header which can be used to ask for compressed transfer. Type: Boolean. Parameter: N/A Notes: More and more websites send their content compressed by default, which is generally a good idea and saves bandwidth. But for the filter, deanimate-gifs and kill-popups actions to work, Privoxy needs access to the uncompressed data. Unfortunately, Privoxy can't yet(!) uncompress, filter, and re-compress the content on the fly. So if you want to ensure that all websites, including those that normally compress, can be filtered, you need to use this action. This will slow down transfers from those websites, though. If you use any of the above-mentioned actions, you will typically want to use prevent-compression in conjunction with them. Note that some (rare) ill-configured sites don't handle requests for uncompressed documents correctly (they send an empty document body). If you use prevent-compression per default, you'll have to add exceptions for those sites. See the example for how to do that. Example usage (sections): # Selectively turn off compression, and enable a filter # { +filter{tiny-textforms} +prevent-compression } # Match only these sites .google. sourceforge.net sf.net # Or instead, we could set a universal default: # { +prevent-compression } / # Match all sites # Then maybe make exceptions for ill-behaved sites: # { -prevent-compression } .debianhelp.org www.pclinuxonline.com ------------------------------------------------------------------------------- 8.5.29. overwrite-last-modified Typical use: Prevent yet another way to track the user's steps between sessions. Effect: Deletes the "Last-Modified:" HTTP server header or modifies its value. Type: Parameterized. Parameter: One of the keywords: "block", "reset-to-request-time" and "randomize" Notes: Removing the "Last-Modified:" header is useful for filter testing, where you want to force a real reload instead of getting status code "304", which would cause the browser to reuse the old version of the page. The "randomize" option overwrites the value of the "Last-Modified:" header with a randomly chosen time between the original value and the current time. In theory the server could send each document with a different "Last-Modified:" header to track visits without using cookies. "Randomize" makes it impossible and the browser can still revalidate cached documents. "reset-to-request-time" overwrites the value of the "Last-Modified:" header with the current time. You could use this option together with hided-if-modified-since to further customize your random range. The preferred parameter here is "randomize". It is safe to use, as long as the time settings are more or less correct. If the server sets the "Last-Modified:" header to the time of the request, the random range becomes zero and the value stays the same. Therefore you should later randomize it a second time with hided-if-modified-since, just to be sure. It is also recommended to use this action together with crunch-if-none-match. Example usage: # Let the browser revalidate without being tracked across sessions { +hide-if-modified-since{-60} \ +overwrite-last-modified{randomize} \ +crunch-if-none-match} / ------------------------------------------------------------------------------- 8.5.30. redirect Typical use: Redirect requests to other sites. Effect: Convinces the browser that the requested document has been moved to another location and the browser should get it from there. Type: Parameterized Parameter: Any URL. Notes: This action is useful to replace whole documents with ones of your choosing. This can be used to enforce safe surfing, or just as a simple convenience. You can do the same by combining the actions block, handle-as-image and set-image-blocker{URL}. It doesn't sound right for non-image documents, and that's why this action was created. This action will be ignored if you use it together with block. Example usages: # Replace example.com's style sheet with another one { +redirect{http://localhost/css-replacements/example.com.css} } example.com/stylesheet.css # Create a short, easy to remember nickname for a favorite site { +redirect{http://www.privoxy.org/user-manual/actions-file.html} } a ------------------------------------------------------------------------------- 8.5.31. send-vanilla-wafer Typical use: Feed log analysis scripts with useless data. Effect: Sends a cookie with each request stating that you do not accept any copyright on cookies sent to you, and asking the site operator not to track you. Type: Boolean. Parameter: N/A Notes: The vanilla wafer is a (relatively) unique header and could conceivably be used to track you. This action is rarely used and not enabled in the default configuration. Example usage: +send-vanilla-wafer ------------------------------------------------------------------------------- 8.5.32. send-wafer Typical use: Send custom cookies or feed log analysis scripts with even more useless data. Effect: Sends a custom, user-defined cookie with each request. Type: Multi-value. Parameter: A string of the form "name=value". Notes: Being multi-valued, multiple instances of this action can apply to the same request, resulting in multiple cookies being sent. This action is rarely used and not enabled in the default configuration. Example usage (section): {+send-wafer{UsingPrivoxy=true}} my-internal-testing-server.void ------------------------------------------------------------------------------- 8.5.33. session-cookies-only Typical use: Allow only temporary "session" cookies (for the current browser session only). Effect: Deletes the "expires" field from "Set-Cookie:" server headers. Most browsers will not store such cookies permanently and forget them in between sessions. Type: Boolean. Parameter: N/A Notes: This is less strict than crunch-incoming-cookies / crunch-outgoing-cookies and allows you to browse websites that insist or rely on setting cookies, without compromising your privacy too badly. Most browsers will not permanently store cookies that have been processed by session-cookies-only and will forget about them between sessions. This makes profiling cookies useless, but won't break sites which require cookies so that you can log in for transactions. This is generally turned on for all sites, and is the recommended setting. It makes no sense at all to use session-cookies-only together with crunch-incoming-cookies or crunch-outgoing-cookies. If you do, cookies will be plainly killed. Note that it is up to the browser how it handles such cookies without an "expires" field. If you use an exotic browser, you might want to try it out to be sure. This setting also has no effect on cookies that may have been stored previously by the browser before starting Privoxy. These would have to be removed manually. Privoxy also uses the content-cookies filter to block some types of cookies. Content cookies are not effected by session-cookies-only. Example usage: +session-cookies-only ------------------------------------------------------------------------------- 8.5.34. set-image-blocker Typical use: Choose the replacement for blocked images Effect: This action alone doesn't do anything noticeable. If both block and handle-as-image also apply, i.e. if the request is to be blocked as an image, then the parameter of this action decides what will be sent as a replacement. Type: Parameterized. Parameter: + "pattern" to send a built-in checkerboard pattern image. The image is visually decent, scales very well, and makes it obvious where banners were busted. + "blank" to send a built-in transparent image. This makes banners disappear completely, but makes it hard to detect where Privoxy has blocked images on a given page and complicates troubleshooting if Privoxy has blocked innocent images, like navigation icons. + "target-url" to send a redirect to target-url. You can redirect to any image anywhere, even in your local filesystem via "file:///" URL. (But note that not all browsers support redirecting to a local file system). A good application of redirects is to use special Privoxy-built-in URLs, which send the built-in images, as target-url. This has the same visual effect as specifying "blank" or "pattern" in the first place, but enables your browser to cache the replacement image, instead of requesting it over and over again. Notes: The URLs for the built-in images are "http://config.privoxy.org/ send-banner?type=type", where type is either "blank" or "pattern". There is a third (advanced) type, called "auto". It is NOT to be used in set-image-blocker, but meant for use from filters. Auto will select the type of image that would have applied to the referring page, had it been an image. Example usage: Built-in pattern: +set-image-blocker{pattern} Redirect to the BSD devil: +set-image-blocker{http://www.freebsd.org/gifs/dae_up3.gif} Redirect to the built-in pattern for better caching: +set-image-blocker{http://config.privoxy.org/send-banner?type=pattern} ------------------------------------------------------------------------------- 8.5.35. treat-forbidden-connects-like-blocks Typical use: Block forbidden connects with an easy to find error message. Effect: If this action is enabled, Privoxy no longer makes a difference between forbidden connects and ordinary blocks. Type: Boolean Parameter: N/A Notes: By default Privoxy answers forbidden "Connect" requests with a short error message inside the headers. If the browser doesn't display headers (most don't), you just see an empty page. With this action enabled, Privoxy displays the message that is used for ordinary blocks instead. If you decide to make an exception for the page in question, you can do so by following the "See why" link. For "Connect" requests the clients tell Privoxy which host they are interested in, but not which document they plan to get later. As a result, the "Go there anyway" link becomes rather useless: it lets the client request the home page of the forbidden host through unencrypted HTTP, still using the port of the last request. If you previously configured Privoxy to do the request through a SSL tunnel, everything will work. Most likely you haven't and the server will respond with an error message because it is expecting HTTPS (SSL). Example usage: +treat-forbidden-connects-like-blocks ------------------------------------------------------------------------------- 8.5.36. Summary Note that many of these actions have the potential to cause a page to misbehave, possibly even not to display at all. There are many ways a site designer may choose to design his site, and what HTTP header content, and other criteria, he may depend on. There is no way to have hard and fast rules for all sites. See the Appendix for a brief example on troubleshooting actions. ------------------------------------------------------------------------------- 8.6. Aliases Custom "actions", known to Privoxy as "aliases", can be defined by combining other actions. These can in turn be invoked just like the built-in actions. Currently, an alias name can contain any character except space, tab, "=", "{" and "}", but we strongly recommend that you only use "a" to "z", "0" to "9", "+", and "-". Alias names are not case sensitive, and are not required to start with a "+" or "-" sign, since they are merely textually expanded. Aliases can be used throughout the actions file, but they must be defined in a special section at the top of the file! And there can only be one such section per actions file. Each actions file may have its own alias section, and the aliases defined in it are only visible within that file. There are two main reasons to use aliases: One is to save typing for frequently used combinations of actions, the other one is a gain in flexibility: If you decide once how you want to handle shops by defining an alias called "shop", you can later change your policy on shops in one place, and your changes will take effect everywhere in the actions file where the "shop" alias is used. Calling aliases by their purpose also makes your actions files more readable. Currently, there is one big drawback to using aliases, though: Privoxy's built-in web-based action file editor honors aliases when reading the actions files, but it expands them before writing. So the effects of your aliases are of course preserved, but the aliases themselves are lost when you edit sections that use aliases with it. Now let's define some aliases... # Useful custom aliases we can use later. # # Note the (required!) section header line and that this section # must be at the top of the actions file! # {{alias}} # These aliases just save typing later: # (Note that some already use other aliases!) # +crunch-all-cookies = +crunch-incoming-cookies +crunch-outgoing-cookies -crunch-all-cookies = -crunch-incoming-cookies -crunch-outgoing-cookies +block-as-image = +block +handle-as-image allow-all-cookies = -crunch-all-cookies -session-cookies-only -filter{content-cookies} # These aliases define combinations of actions # that are useful for certain types of sites: # fragile = -block -filter -crunch-all-cookies -fast-redirects -hide-referrer -kill-popups -prevent-compression shop = -crunch-all-cookies -filter{all-popups} -kill-popups # Short names for other aliases, for really lazy people ;-) # c0 = +crunch-all-cookies c1 = -crunch-all-cookies ...and put them to use. These sections would appear in the lower part of an actions file and define exceptions to the default actions (as specified further up for the "/" pattern): # These sites are either very complex or very keen on # user data and require minimal interference to work: # {fragile} .office.microsoft.com .windowsupdate.microsoft.com # Gmail is really mail.google.com, not gmail.com mail.google.com # Shopping sites: # Allow cookies (for setting and retrieving your customer data) # {shop} .quietpc.com .worldpay.com # for quietpc.com mybank.example.com # These shops require pop-ups: # {-kill-popups -filter{all-popups} -filter{unsolicited-popups}} .dabs.com .overclockers.co.uk Aliases like "shop" and "fragile" are typically used for "problem" sites that require more than one action to be disabled in order to function properly. ------------------------------------------------------------------------------- 8.7. Actions Files Tutorial The above chapters have shown which actions files there are and how they are organized, how actions are specified and applied to URLs, how patterns work, and how to define and use aliases. Now, let's look at an example default.action and user.action file and see how all these pieces come together: ------------------------------------------------------------------------------- 8.7.1. default.action Every config file should start with a short comment stating its purpose: # Sample default.action file Then, since this is the default.action file, the first section is a special section for internal use that you needn't change or worry about: ########################################################################## # Settings -- Don't change! For internal Privoxy use ONLY. ########################################################################## {{settings}} for-privoxy-version=3.0 After that comes the (optional) alias section. We'll use the example section from the above chapter on aliases, that also explains why and how aliases are used: ########################################################################## # Aliases ########################################################################## {{alias}} # These aliases just save typing later: # (Note that some already use other aliases!) # +crunch-all-cookies = +crunch-incoming-cookies +crunch-outgoing-cookies -crunch-all-cookies = -crunch-incoming-cookies -crunch-outgoing-cookies +block-as-image = +block +handle-as-image mercy-for-cookies = -crunch-all-cookies -session-cookies-only -filter{content-cookies} # These aliases define combinations of actions # that are useful for certain types of sites: # fragile = -block -filter -crunch-all-cookies -fast-redirects -hide-referrer -kill-popups shop = -crunch-all-cookies -filter{all-popups} -kill-popups Now come the regular sections, i.e. sets of actions, accompanied by URL patterns to which they apply. Remember all actions are disabled when matching starts, so we have to explicitly enable the ones we want. The first regular section is probably the most important. It has only one pattern, "/", but this pattern matches all URLs. Therefore, the set of actions used in this "default" section will be applied to all requests as a start. It can be partly or wholly overridden by later matches further down this file, or in user.action, but it will still be largely responsible for your overall browsing experience. Again, at the start of matching, all actions are disabled, so there is no real need to disable any actions here, but we will do that nonetheless, to have a complete listing for your reference. (Remember: a "+" preceding the action name enables the action, a "-" disables!). Also note how this long line has been made more readable by splitting it into multiple lines with line continuation. ########################################################################## # "Defaults" section: ########################################################################## { \ -add-header \ -block \ -content-type-overwrite \ -crunch-client-header \ -crunch-if-none-match \ -crunch-incoming-cookies \ -crunch-server-header \ -crunch-outgoing-cookies \ +deanimate-gifs \ -downgrade-http-version \ -fast-redirects{check-decoded-url} \ -filter{js-annoyances} \ -filter{js-events} \ +filter{html-annoyances} \ -filter{content-cookies} \ +filter{refresh-tags} \ -filter{unsolicited-popups} \ -filter{all-popups} \ -filter{img-reorder} \ -filter{banners-by-size} \ -filter{banners-by-link} \ +filter{webbugs} \ -filter{tiny-textforms} \ -filter{jumping-windows} \ -filter{frameset-borders} \ -filter{demoronizer} \ -filter{shockwave-flash} \ -filter{quicktime-kioskmode} \ -filter{fun} \ -filter{crude-parental} \ +filter{ie-exploits} \ -filter-client-headers \ -filter-server-headers \ -filter-google \ -filter-yahoo \ -filter-msn \ -filter-blogspot \ -filter-xml-to-html \ -filter-html-to-xml \ -filter-no-ping \ -filter-hide-tor-exit-notation \ -force-text-mode \ -handle-as-empty-document \ -handle-as-image \ -hide-accept-language \ -hide-content-disposition \ -hide-if-modified-since \ +hide-forwarded-for-headers \ +hide-from-header{block} \ +hide-referrer{forge} \ -hide-user-agent \ -inspect-jpegs \ -kill-popups \ -limit-connect \ +prevent-compression \ -overwrite-last-modified \ -redirect \ -send-vanilla-wafer \ -send-wafer \ +session-cookies-only \ +set-image-blocker{pattern} \ -treat-forbidden-connects-like-blocks \ } / # forward slash will match *all* potential URL patterns. The default behavior is now set. Note that some actions, like not hiding the user agent, are part of a "general policy" that applies universally and won't get any exceptions defined later. Other choices, like not blocking (which is understandably the default!) need exceptions, i.e. we need to specify explicitly what we want to block in later sections. The first of our specialized sections is concerned with "fragile" sites, i.e. sites that require minimum interference, because they are either very complex or very keen on tracking you (and have mechanisms in place that make them unusable for people who avoid being tracked). We will simply use our pre-defined fragile alias instead of stating the list of actions explicitly: ########################################################################## # Exceptions for sites that'll break under the default action set: ########################################################################## # "Fragile" Use a minimum set of actions for these sites (see alias above): # { fragile } .office.microsoft.com # surprise, surprise! .windowsupdate.microsoft.com mail.google.com Shopping sites are not as fragile, but they typically require cookies to log in, and pop-up windows for shopping carts or item details. Again, we'll use a pre-defined alias: # Shopping sites: # { shop } .quietpc.com .worldpay.com # for quietpc.com .jungle.com .scan.co.uk The fast-redirects action, which we enabled per default above, breaks some sites. So disable it for popular sites where we know it misbehaves: { -fast-redirects } login.yahoo.com edit.*.yahoo.com .google.com .altavista.com/.*(like|url|link):http .altavista.com/trans.*urltext=http .nytimes.com It is important that Privoxy knows which URLs belong to images, so that if they are to be blocked, a substitute image can be sent, rather than an HTML page. Contacting the remote site to find out is not an option, since it would destroy the loading time advantage of banner blocking, and it would feed the advertisers (in terms of money and information). We can mark any URL as an image with the handle-as-image action, and marking all URLs that end in a known image file extension is a good start: ########################################################################## # Images: ########################################################################## # Define which file types will be treated as images, in case they get # blocked further down this file: # { +handle-as-image } /.*\.(gif|jpe?g|png|bmp|ico)$ And then there are known banner sources. They often use scripts to generate the banners, so it won't be visible from the URL that the request is for an image. Hence we block them and mark them as images in one go, with the help of our +block-as-image alias defined above. (We could of course just as well use + block +handle-as-image here.) Remember that the type of the replacement image is chosen by the set-image-blocker action. Since all URLs have matched the default section with its +set-image-blocker{pattern} action before, it still applies and needn't be repeated: # Known ad generators: # { +block-as-image } ar.atwola.com .ad.doubleclick.net .ad.*.doubleclick.net .a.yimg.com/(?:(?!/i/).)*$ .a[0-9].yimg.com/(?:(?!/i/).)*$ bs*.gsanet.com .qkimg.net One of the most important jobs of Privoxy is to block banners. Many of these can be "blocked" by the filter{banners-by-size} action, which we enabled above, and which deletes the references to banner images from the pages while they are loaded, so the browser doesn't request them anymore, and hence they don't need to be blocked here. But this naturally doesn't catch all banners, and some people choose not to use filters, so we need a comprehensive list of patterns for banner URLs here, and apply the block action to them. First comes many generic patterns, which do most of the work, by matching typical domain and path name components of banners. Then comes a list of individual patterns for specific sites, which is omitted here to keep the example short: ########################################################################## # Block these fine banners: ########################################################################## { +block } # Generic patterns: # ad*. .*ads. banner?. count*. /.*count(er)?\.(pl|cgi|exe|dll|asp|php[34]?) /(?:.*/)?(publicite|werbung|rekla(ma|me|am)|annonse|maino(kset|nta|s)?)/ # Site-specific patterns (abbreviated): # .hitbox.com It's quite remarkable how many advertisers actually call their banner servers ads.company.com, or call the directory in which the banners are stored simply "banners". So the above generic patterns are surprisingly effective. But being very generic, they necessarily also catch URLs that we don't want to block. The pattern .*ads. e.g. catches "nasty-ads.nasty-corp.com" as intended, but also "downloads.sourcefroge.net" or "adsl.some-provider.net." So here come some well-known exceptions to the +block section above. Note that these are exceptions to exceptions from the default! Consider the URL "downloads.sourcefroge.net": Initially, all actions are deactivated, so it wouldn't get blocked. Then comes the defaults section, which matches the URL, but just deactivates the block action once again. Then it matches .*ads., an exception to the general non-blocking policy, and suddenly +block applies. And now, it'll match .*loads., where -block applies, so (unless it matches again further down) it ends up with no block action applying. ########################################################################## # Save some innocent victims of the above generic block patterns: ########################################################################## # By domain: # { -block } adv[io]*. # (for advogato.org and advice.*) adsl. # (has nothing to do with ads) adobe. # (has nothing to do with ads either) ad[ud]*. # (adult.* and add.*) .edu # (universities don't host banners (yet!)) .*loads. # (downloads, uploads etc) # By path: # /.*loads/ # Site-specific: # www.globalintersec.com/adv # (adv = advanced) www.ugu.com/sui/ugu/adv Filtering source code can have nasty side effects, so make an exception for our friends at sourceforge.net, and all paths with "cvs" in them. Note that -filter disables all filters in one fell swoop! # Don't filter code! # { -filter } /(.*/)?cvs bugzilla. developer. wiki. .sourceforge.net The actual default.action is of course much more comprehensive, but we hope this example made clear how it works. ------------------------------------------------------------------------------- 8.7.2. user.action So far we are painting with a broad brush by setting general policies, which would be a reasonable starting point for many people. Now, you might want to be more specific and have customized rules that are more suitable to your personal habits and preferences. These would be for narrowly defined situations like your ISP or your bank, and should be placed in user.action, which is parsed after all other actions files and hence has the last word, over-riding any previously defined actions. user.action is also a safe place for your personal settings, since default.action is actively maintained by the Privoxy developers and you'll probably want to install updated versions from time to time. So let's look at a few examples of things that one might typically do in user.action: # My user.action file. As aliases are local to the actions file that they are defined in, you can't use the ones from default.action, unless you repeat them here: # Aliases are local to the file they are defined in. # (Re-)define aliases for this file: # {{alias}} # # These aliases just save typing later, and the alias names should # be self explanatory. # +crunch-all-cookies = +crunch-incoming-cookies +crunch-outgoing-cookies -crunch-all-cookies = -crunch-incoming-cookies -crunch-outgoing-cookies allow-all-cookies = -crunch-all-cookies -session-cookies-only allow-popups = -filter{all-popups} -kill-popups +block-as-image = +block +handle-as-image -block-as-image = -block # These aliases define combinations of actions that are useful for # certain types of sites: # fragile = -block -crunch-all-cookies -filter -fast-redirects -hide-referrer -kill-popups shop = -crunch-all-cookies allow-popups # Allow ads for selected useful free sites: # allow-ads = -block -filter{banners-by-size} -filter{banners-by-link} # Alias for specific file types that are text, but might have conflicting # MIME types. We want the browser to force these to be text documents. handle-as-text = -filter +-content-type-overwrite{text/plain} +-force-text-mode -hide-content-disposition Say you have accounts on some sites that you visit regularly, and you don't want to have to log in manually each time. So you'd like to allow persistent cookies for these sites. The allow-all-cookies alias defined above does exactly that, i.e. it disables crunching of cookies in any direction, and the processing of cookies to make them only temporary. { allow-all-cookies } sourceforge.net .yahoo.com .msdn.microsoft.com .redhat.com Your bank is allergic to some filter, but you don't know which, so you disable them all: { -filter } .your-home-banking-site.com Some file types you may not want to filter for various reasons: # Technical documentation is likely to contain strings that might # erroneously get altered by the JavaScript-oriented filters: # .tldp.org /(.*/)?selfhtml/ # And this stupid host sends streaming video with a wrong MIME type, # so that Privoxy thinks it is getting HTML and starts filtering: # stupid-server.example.com/ Example of a simple block action. Say you've seen an ad on your favourite page on example.com that you want to get rid of. You have right-clicked the image, selected "copy image location" and pasted the URL below while removing the leading http://, into a { +block } section. Note that { +handle-as-image } need not be specified, since all URLs ending in .gif will be tagged as images by the general rules as set in default.action anyway: { +block } www.example.com/nasty-ads/sponsor.gif another.popular.site.net/more/junk/here/ The URLs of dynamically generated banners, especially from large banner farms, often don't use the well-known image file name extensions, which makes it impossible for Privoxy to guess the file type just by looking at the URL. You can use the +block-as-image alias defined above for these cases. Note that objects which match this rule but then turn out NOT to be an image are typically rendered as a "broken image" icon by the browser. Use cautiously. { +block-as-image } .doubleclick.net .fastclick.net /Realmedia/ads/ ar.atwola.com/ Now you noticed that the default configuration breaks Forbes Magazine, but you were too lazy to find out which action is the culprit, and you were again too lazy to give feedback, so you just used the fragile alias on the site, and -- whoa! -- it worked. The fragile aliases disables those actions that are most likely to break a site. Also, good for testing purposes to see if it is Privoxy that is causing the problem or not. We later find other regular sites that misbehave, and add those to our personalized list of troublemakers: { fragile } .forbes.com webmail.example.com .mybank.com You like the "fun" text replacements in default.filter, but it is disabled in the distributed actions file. (My colleagues on the team just don't have a sense of humour, that's why! ;-). So you'd like to turn it on in your private, update-safe config, once and for all: { +filter{fun} } / # For ALL sites! Note that the above is not really a good idea: There are exceptions to the filters in default.action for things that really shouldn't be filtered, like code on CVS->Web interfaces. Since user.action has the last word, these exceptions won't be valid for the "fun" filtering specified here. You might also worry about how your favourite free websites are funded, and find that they rely on displaying banner advertisements to survive. So you might want to specifically allow banners for those sites that you feel provide value to you: { allow-ads } .sourceforge.net .slashdot.org .osdn.net Note that allow-ads has been aliased to -block, -filter{banners-by-size}, and - filter{banners-by-link} above. Invoke another alias here to force an over-ride of the MIME type application/ x-sh which typically would open a download type dialog. In my case, I want to look at the shell script, and then I can save it should I choose to. { handle-as-text } /.*\.sh$ user.action is generally the best place to define exceptions and additions to the default policies of default.action. Some actions are safe to have their default policies set here though. So let's set a default policy to have a "blank" image as opposed to the checkerboard pattern for ALL sites. "/" of course matches all URL paths and patterns: { +set-image-blocker{blank} } / # ALL sites ------------------------------------------------------------------------------- 9. Filter Files On-the-fly text substitutions that can be invoked through the filter action need to be defined in a "filter file". Once defined, they can then be invoked as an "action". Multiple filter files can be defined through the filterfile config directive. The filters as supplied by the developers will be found in default.filter. It is recommended that any locally defined or modified filters go in a separately defined file such as user.filter. Typical reasons for doing these kinds of substitutions are to eliminate common annoyances in HTML and JavaScript, such as pop-up windows, exit consoles, crippled windows without navigation tools, the infamous tag etc, to suppress images with certain width and height attributes (standard banner sizes or web-bugs), or just to have fun. The possibilities are endless. Filtering works on any text-based document type, including HTML, JavaScript, CSS etc. (all text/* MIME types, except text/plain). Substitutions are made at the source level, so if you want to "roll your own" filters, you should first be familiar with HTML syntax, and, of course, regular expressions. By default, filters are only applied to the raw document content, but can be extended to the HTTP headers with the supplemental actions: filter-client-headers and filter-server-headers. Just like the actions files, the filter file is organized in sections, which are called filters here. Each filter consists of a heading line, that starts with the keyword FILTER:, followed by the filter's name, and a short (one line) description of what it does. Below that line come the jobs, i.e. lines that define the actual text substitutions. By convention, the name of a filter should describe what the filter eliminates. The comment is used in the web-based user interface. Once a filter called name has been defined in the filter file, it can be invoked by using an action of the form +filter{name} in any actions file. A filter header line for a filter called "foo" could look like this: FILTER: foo Replace all "foo" with "bar" Below that line, and up to the next header line, come the jobs that define what text replacements the filter executes. They are specified in a syntax that imitates Perl's s/// operator. If you are familiar with Perl, you will find this to be quite intuitive, and may want to look at the PCRS documentation for the subtle differences to Perl behaviour. Most notably, the non-standard option letter U is supported, which turns the default to ungreedy matching. If you are new to "Regular Expressions", you might want to take a look at the Appendix on regular expressions, and see the Perl manual for the s/// operator's syntax and Perl-style regular expressions in general. The below examples might also help to get you started. ------------------------------------------------------------------------------- 9.1. Filter File Tutorial Now, let's complete our "foo" filter. We have already defined the heading, but the jobs are still missing. Since all it does is to replace "foo" with "bar", there is only one (trivial) job needed: s/foo/bar/ But wait! Didn't the comment say that all occurrences of "foo" should be replaced? Our current job will only take care of the first "foo" on each page. For global substitution, we'll need to add the g option: s/foo/bar/g Our complete filter now looks like this: FILTER: foo Replace all "foo" with "bar" s/foo/bar/g Let's look at some real filters for more interesting examples. Here you see a filter that protects against some common annoyances that arise from JavaScript abuse. Let's look at its jobs one after the other: FILTER: js-annoyances Get rid of particularly annoying JavaScript abuse # Get rid of JavaScript referrer tracking. Test page: http://www.randomoddness.com/untitled.htm # s|()|$1"Not Your Business!"$2|Usg Following the header line and a comment, you see the job. Note that it uses | as the delimiter instead of /, because the pattern contains a forward slash, which would otherwise have to be escaped by a backslash (\). Now, let's examine the pattern: it starts with the text tag. That's more than we want, but the pattern continues: document\.referrer matches only the exact string "document.referrer". The dot needed to be escaped, i.e. preceded by a backslash, to take away its special meaning as a joker, and make it just a regular dot. So far, the meaning is: Match from the start of the first . You already know what .* means, so the whole pattern translates to: Match from the start of the first " tag. Furthermore, the s option says that the match may span multiple lines in the page, and the g option again means that the substitution is global. So, to summarize, the pattern means: Match all scripts that contain the text "document.referrer". Remember the parts of the script from (and including) the start tag up to (and excluding) the string "document.referrer" as $1, and the part following that string, up to and including the closing tag, as $2. Now the pattern is deciphered, but wasn't this about substituting things? So lets look at the substitute: $1"Not Your Business!"$2 is easy to read: The text remembered as $1, followed by "Not Your Business!" (including the quotation marks!), followed by the text remembered as $2. This produces an exact copy of the original string, with the middle part (the "document.referrer") replaced by "Not Your Business!". The whole job now reads: Replace "document.referrer" by "Not Your Business!" wherever it appears inside a