Privoxy User Manual Copyright © 2001, 2002 by Privoxy Developers $Id: user-manual.sgml,v 1.111 2002/05/14 23:01:36 oes Exp $ The 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, filtering web page content, 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 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, SuSE RPMs and Conectiva 2.1.2. Debian 2.1.3. Windows 2.1.4. Solaris, NetBSD, FreeBSD, HP-UX 2.1.5. OS/2 2.1.6. Max OSX 2.1.7. AmigaOS 2.2. Building from Source 3. Note to Upgraders 4. Quickstart to Using Privoxy 5. Starting Privoxy 5.1. RedHat, Conectiva and Debian 5.2. SuSE 5.3. Windows 5.4. Solaris, NetBSD, FreeBSD, HP-UX and others 5.5. OS/2 5.6. MAX OSX 5.7. AmigaOS 5.8. 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. Configuration and Log File Locations 7.1.1. confdir 7.1.2. logdir 7.1.3. actionsfile 7.1.4. filterfile 7.1.5. logfile 7.1.6. jarfile 7.1.7. trustfile 7.2. Local Set-up Documentation 7.2.1. user-manual 7.2.2. trust-info-url 7.2.3. admin-address 7.2.4. proxy-info-url 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-edit-actions 7.4.5. ACLs: permit-access and deny-access 7.4.6. buffer-limit 7.5. Forwarding 7.5.1. forward 7.5.2. forward-socks4 and forward-socks4a 7.5.3. Advanced Forwarding Examples 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. crunch-incoming-cookies 8.5.4. crunch-outgoing-cookies 8.5.5. deanimate-gifs 8.5.6. downgrade-http-version 8.5.7. fast-redirects 8.5.8. filter 8.5.9. handle-as-image 8.5.10. hide-forwarded-for-headers 8.5.11. hide-from-header 8.5.12. hide-referrer 8.5.13. hide-user-agent 8.5.14. kill-popups 8.5.15. limit-connect 8.5.16. prevent-compression 8.5.17. send-vanilla-wafer 8.5.18. send-wafer 8.5.19. session-cookies-only 8.5.20. set-image-blocker 8.5.21. Summary 8.6. Aliases 8.7. Sample Actions Files 9. The Filter File 9.1. The +filter Action 10. Templates 11. Contacting the Developers, Bug Reporting and Feature Requests 11.1. Get Support 11.2. Report bugs 11.3. Request new features 11.4. Report ads or other filter problems 11.5. Other 12. Privoxy Copyright, License and History 12.1. License 12.2. History 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. Anatomy of an Action 1. Introduction This documentation is included with the current beta version of Privoxy, v.2.9.15, and is mostly complete at this point. The most up to date reference for the time being is still the comments in the source files and in the individual configuration files. Development of version 3.0 is currently nearing completion, and includes many significant changes and enhancements over earlier versions. The target release date for stable v3.0 is "soon" ;-). Since this is a beta version, not all new features are well tested. This documentation may be slightly out of sync as a result (especially with CVS sources). And there may be bugs, though hopefully not many! ------------------------------------------------------------------------------- 1.1. Features In addition to Internet Junkbuster's traditional features of ad and banner blocking and cookie management, Privoxy provides new features, some of them currently under development: * 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 content filtering (removes banners based on size, invisible "web-bugs", JavaScript and HTML annoyances, pop-up windows, 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: If you have a previous Junkbuster or Privoxy installation on your system, you will need to remove it. On some platforms, this may be done for you as part of their installation procedure. (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, SuSE RPMs and Conectiva RPMs can be installed with rpm -Uvh privoxy-2.9.15-1.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. Note that SuSE will automatically start Privoxy in the boot process. If you have problems with failed dependencies, try rebuilding the SRC RPM: rpm --rebuild privoxy-2.9.15-1.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, before installing Privoxy. ------------------------------------------------------------------------------- 2.1.2. Debian FIXME. ------------------------------------------------------------------------------- 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. We do not use the registry of Windows. ------------------------------------------------------------------------------- 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. FIXME. ------------------------------------------------------------------------------- 2.1.5. OS/2 First, make sure that no previous installations of Junkbuster and / or Privoxy are left on your system. You can do this by 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. Max OSX Unzip the downloaded package (you can either double-click on the file in the finder, or on the desktop if you downloaded it there). Then, double-click on the package installer icon and follow the installation process. Privoxy will be installed in the subdirectory /Applications/Privoxy.app. Privoxy will set itself up to start automatically on system bring-up via /System/Library/ StartupItems/Privoxy. ------------------------------------------------------------------------------- 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. 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). ------------------------------------------------------------------------------- 2.2. Building from Source The most convenient way to obtain the Privoxy sources is to download the source tarball from our project 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 or simply download the nightly CVS tarball. 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 (either release version or nightly CVS tarball), first unpack the source: tar xzvf privoxy-2.9.15-beta-src* [.tgz or .tar.gz] cd privoxy-2.9.15-beta For retrieving the current CVS sources, you'll need CVS installed. Note that sources from CVS are development quality, and may not be stable, or well tested. To download CVS source: cvs -d:pserver:anonymous@cvs.ijbswa.sourceforge.net:/cvsroot/ijbswa login cvs -z3 -d:pserver:anonymous@cvs.ijbswa.sourceforge.net:/cvsroot/ijbswa co current cd current This will create a directory named current/, which will contain the source tree. Then, in either case, to build from unpacked tarball or CVS source: autoheader autoconf ./configure # (--help to see options) make # (the make from gnu, gmake for *BSD) su make -n install # (to see where all the files will go) make install # (to really install) If you have 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. For more detailed instructions on how to build Redhat and SuSE RPMs, Windows self-extracting installers, building on platforms with special requirements etc, please consult the developer manual. ------------------------------------------------------------------------------- 3. Note to Upgraders There are very significant changes from earlier Junkbuster versions to the current Privoxy. The number, names, syntax, and purposes of configuration files have substantially changed. Junkbuster 2.0.x configuration files will not migrate, Junkbuster 2.9.x and Privoxy configurations will need to be ported. The functionalities of the old blockfile, cookiefile and imagelist are now combined into the "actions files". default.action, is the main actions file. Local exceptions should best be put into user.action. A "filter file" (typically default.filter) is new as of Privoxy 2.9.x, and provides some of the new sophistication (explained below). config is much the same as before. If upgrading from a 2.0.x version, you will have to use the new config files, and possibly adapt any personal rules from your older files. When porting personal rules over from the old blockfile to the new actions files, please note that even the pattern syntax has changed. If upgrading from 2.9.x development versions, it is still recommended to use the new configuration files. A quick list of things to be aware of before upgrading: * The default listening port is now 8118 due to a conflict with another service (NAS). * Some installers may remove earlier versions completely. Save any important configuration files! * Privoxy is controllable with a web browser at the special URL: http:// config.privoxy.org/ (Shortcut: http://p.p/). Many aspects of configuration can be done here, including temporarily disabling Privoxy. * The primary configuration file for cookie management, ad and banner blocking, and many other aspects of Privoxy configuration is in the actions files. It is strongly recommended to become familiar with the new actions concept below, before modifying these files. Locally defined rules should go into user.action. * Some installers may not automatically start Privoxy after installation. ------------------------------------------------------------------------------- 4. Quickstart to Using Privoxy * If upgrading, please back up any configuration files. See the Note to Upgraders Section. * Install Privoxy. See the Installation Section for platform specific information. * Start Privoxy, if the installation program has not done this already. See the section Starting Privoxy. * Set your browser to use Privoxy as HTTP and HTTPS proxy by setting the proxy configuration for address of 127.0.0.1 and port 8118. (Junkbuster and earlier versions of Privoxy used port 8000.) See the section Starting Privoxy. * Flush your browser's caches, to remove any cached ad images. * Enjoy surfing with enhanced comfort and privacy. You may want to customize the user.action file to personalize your new browsing experience. See the Configuration section for more configuration options, and how to further customize your installation. * If you experience problems with sites that "misbehave", see the Anatomy of an Action section in the Appendix. * Please see the section Contacting the Developers on how to report bugs or problems with websites or to get help. ------------------------------------------------------------------------------- 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 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! With Netscape (and Mozilla), this can be set under Edit -> Preferences -> Advanced -> Proxies -> HTTP Proxy. For Internet Explorer: Tools -> Internet Properties -> Connections -> LAN Setting. Then, check "Use Proxy" and fill in the appropriate info (Address: 127.0.0.1, Port: 8118). Include if HTTPS proxy support too. 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. You are now ready to start enjoying the benefits of using Privoxy! Privoxy 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. RedHat, Conectiva and Debian We use a script. Note that RedHat does not start Privoxy upon booting per default. It will use the file /etc/privoxy/config as its main configuration file. FIXME: Debian?? # /etc/rc.d/init.d/privoxy start ------------------------------------------------------------------------------- 5.2. SuSE We use a script. It will use the file /etc/privoxy/config as its main configuration file. Note that SuSE starts Privoxy upon booting your PC. # rcprivoxy 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 upon booting you PC. ------------------------------------------------------------------------------- 5.4. Solaris, NetBSD, FreeBSD, HP-UX and others Example Unix startup command: # /usr/sbin/privoxy /etc/privoxy/config ------------------------------------------------------------------------------- 5.5. OS/2 FIXME. ------------------------------------------------------------------------------- 5.6. MAX OSX FIXME. ------------------------------------------------------------------------------- 5.7. AmigaOS FIXME. ------------------------------------------------------------------------------- 5.8. 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. * 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. ------------------------------------------------------------------------------- 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 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 name and number of configuration files has changed from previous versions, and is subject to change as development progresses. 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 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. * default.filter (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. 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. The actions files and default.filter 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. While under development, the configuration content is subject to change. The below documentation may not be accurate by the time you read this. Also, what constitutes a "default" setting, may change, so please check all your configuration files on important issues. ------------------------------------------------------------------------------- 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. 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. ------------------------------------------------------------------------------- 7.1.1. 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 When development goes modular and multi-user, the blocker, filter, and per-user config will be stored in subdirectories of "confdir". For now, the configuration directory structure is flat, except for confdir/templates, where the HTML templates for CGI output reside (e.g. Privoxy's 404 error page). ------------------------------------------------------------------------------- 7.1.2. 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 ------------------------------------------------------------------------------- 7.1.3. actionsfile Specifies: The actions file(s) to use Type of value: File name, relative to confdir, without the .action suffix Default value: 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. ------------------------------------------------------------------------------- 7.1.4. filterfile Specifies: The filter file 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: The "default.filter" file contains content modification rules that use "regular expressions". These rules permit powerful changes on the content of Web pages, e.g., you could disable your favorite JavaScript annoyances, re-write the actual displayed text, or just have some fun replacing "Microsoft" with "MicroSuck" wherever it appears on a Web page. ------------------------------------------------------------------------------- 7.1.5. 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 windows version will additionally log to the console. 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"). ------------------------------------------------------------------------------- 7.1.6. jarfile Specifies: The file to store intercepted cookies in Type of value: File name, relative to logdir Default value: jarfile (Unix) or privoxy.jar (Windows) Effect if unset: Intercepted cookies are not stored at all. Notes: The jarfile may grow to ridiculous sizes over time. ------------------------------------------------------------------------------- 7.1.7. trustfile Specifies: 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 whole trust mechanism is turned off. 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 named in the trustfile. You can also mark sites as trusted referrers (with +), with the effect that access to untrusted sites will be granted, if a link from a trusted referrer was used. The link target will then be added to the "trustfile". Possible applications include limiting Internet access for children. If you use + operator in the trust file, it may grow considerably over time. ------------------------------------------------------------------------------- 7.2. 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. ------------------------------------------------------------------------------- 7.2.1. 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 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. For multi-user setups, you could provide a copy on a local webserver for all your users and use the corresponding URL here. Examples: Unix, in local filesystem: user-manual file:///usr/share/doc/privoxy-2.9.15/user-manual/ Any platform, on local webserver (called "local-webserver"): user-manual http://local-webserver/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. | +-----------------------------------------------------------------+ ------------------------------------------------------------------------------- 7.2.2. 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! ------------------------------------------------------------------------------- 7.2.3. 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. ------------------------------------------------------------------------------- 7.2.4. 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 ;-) ------------------------------------------------------------------------------- 7.3. 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 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 "ACLs" below), or a firewall. 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-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. ------------------------------------------------------------------------------- 7.4.5. 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 ------------------------------------------------------------------------------- 7.4.6. 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 (see e.g. http://www.multiproxy.org/anon_list.htm) 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_domain[:port] http_parent[/port] Where target_domain is a domain name pattern (see the chapter on domain matching in the default.action file), http_parent is the address of the parent HTTP proxy as an IP addresses in dotted decimal notation or as a valid DNS name (or "." to denote "no 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 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_domain[:port] socks_proxy[/port] http_parent[/port] Where target_domain is a domain name pattern (see the chapter on domain matching in the default.action file), 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 . ------------------------------------------------------------------------------- 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. ------------------------------------------------------------------------------- 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 determine 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 three such files included with Privoxy (as of version 2.9.15), with differing purposes: * standard.action - is used by the web based editor, to set various pre-defined sets of rules for the default actions section in default.action. These have increasing levels of aggressiveness and have no influence on your browsing unless you select them explicitly in the editor. It is not recommend to edit this file. * 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 for users everywhere. This is the file that the developers are keeping updated, and making available to users. * 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. The list of actions files to be used are defined in the main configuration file, and are processed in the order they are defined. The content of these can all be viewed and edited from http://config.privoxy.org/show-status. 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. 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 kill popup windows per default, you'll have to make exceptions from that rule for sites that you regularly use and that require popups for actually useful content, 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". If you prefer plain text editing to GUIs, you can of course also directly edit the the actions files. Look at default.action which is richly commented. ------------------------------------------------------------------------------- 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 both the "+handle-as-image" and "+block" actions). You can trace this process for any given URL by visiting http:// config.privoxy.org/show-url-info. More detail on this is provided in the Appendix, Anatomy of an Action. ------------------------------------------------------------------------------- 8.4. Patterns Generally, a pattern has the form /, where both the and are optional. (This is why the pattern / matches all URLs). 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. 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. index.html matches nothing, since it would be interpreted as a domain name and there is no top-level domain called .html. ------------------------------------------------------------------------------- 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. (Correctly speaking: It matches any FQDN that contains example as a domain.) Additionally, there are wild-cards that you can use in the domain names themselves. They work pretty similar to shell wild-cards: "*" stands for zero or more arbitrary characters, "?" stands for any single character, you can define character classes in square brackets and all of that 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. ------------------------------------------------------------------------------- 8.4.2. The Path Pattern Privoxy uses Perl compatible regular expressions (through the PCRE library) for matching the path. 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:// www.perldoc.com/perl5.6/pod/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. ------------------------------------------------------------------------------- 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. There are three classes of actions: * 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). 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 pattern to match more than one pattern and thus more than one set of actions! 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 obnoxious content Effect: Requests for URLs to which this action applies are blocked, i.e. the requests are not forwarded to the remote server, but answered locally with a substitute page or image, as determined by the handle-as-image and set-image-blocker 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. 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 ------------------------------------------------------------------------------- 8.5.3. 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. Example usage: +crunch-incoming-cookies ------------------------------------------------------------------------------- 8.5.4. 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 ------------------------------------------------------------------------------- 8.5.5. 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} ------------------------------------------------------------------------------- 8.5.6. 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 ------------------------------------------------------------------------------- 8.5.7. fast-redirects Typical use: Fool some click-tracking scripts and speed up indirect links Effect: Cut off all but the last valid URL from requests. Type: Boolean. Parameter: N/A 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://some.place/click-tracker.cgi? target=http://some.where.else. 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 ask 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. It is likely to break some sites. You should expect to need possibly many exceptions to this action, if it is enabled by default in default.action. Some sites just don't work without it. Example usage: {+fast-redirects} ------------------------------------------------------------------------------- 8.5.8. filter Typical use: Get rid of HTML and JavaScript annoyances, banner advertisements (by size), do fun text replacements, etc. Effect: Text documents, including HTML and JavaScript, to which this action applies, are filtered on-the-fly through the specified regular expression based substitutions. Type: Parameterized. Parameter: The name of a filter, as defined in the filter file (typically default.filter, set by the filterfile option in the config file) Notes: For your convenience, there are a bunch of pre-defined filters available in the distribution filter file that you can use. See the example below for a list. This is potentially a very powerful feature! But "rolling your own" filters requires a knowledge of regular expressions and HTML. 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. At this time, Privoxy cannot (yet!) uncompress compressed documents. If you want filtering to work on all documents, even those that would normally be sent compressed, use the prevent-compression action in conjunction with filter. Filtering can achieve some of the effects as the block action, i.e. it can be used to block ads and banners. Feedback with suggestions for new or improved filters is particularly welcome! Example usage (with filters from the distribution default.filter file): +filter{html-annoyances} # Get rid of particularly annoying HTML abuse. +filter{js-annoyances} # Get rid of particularly annoying JavaScript abuse +filter{banners-by-size} # Kill banners by size (very efficient!) +filter{content-cookies} # Kill cookies that come sneaking in the HTML or JS content +filter{popups} # Kill all popups in JS and HTML +filter{webbugs} # Squish WebBugs (1x1 invisible GIFs used for user tracking) +filter{fun} # Text replacements for subversive browsing fun! +filter{frameset-borders} # Give frames a border and make them resizeable +filter{refresh-tags} # Kill automatic refresh tags (for dial-on-demand setups) +filter{nimda} # Remove Nimda (virus) code. +filter{shockwave-flash} # Kill embedded Shockwave Flash objects +filter{crude-parental} # Kill all web pages that contain the words "sex" or "warez" ------------------------------------------------------------------------------- 8.5.9. handle-as-image Typical use: Mark URLs as belonging to images (so they'll be replaced by images if they get blocked) 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, (inline) 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 ------------------------------------------------------------------------------- 8.5.10. 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 ------------------------------------------------------------------------------- 8.5.11. 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} ------------------------------------------------------------------------------- 8.5.12. 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: + "block" to delete the header completely. + "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: "forge" is the preferred option here, since some servers will not send images back otherwise, in an attempt to prevent their valuable content from being embedded elsewhere (and hence, without being surrounded by their banners). 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/} ------------------------------------------------------------------------------- 8.5.13. 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 breaks many web sites that depend on looking at this header | |in order to customize their content for different browsers | |(which, by the way, is NOT a smart way to do that!). | +-----------------------------------------------------------------+ 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)} ------------------------------------------------------------------------------- 8.5.14. kill-popups Typical use: Eliminate those annoying pop-up windows 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 easily confused with the built-in, hardwired 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{popups} does. 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 it's filter equivalent. Killing all pop-ups is a dangerous business. Many shops and banks rely on pop-ups to display forms, shopping carts etc, and killing only the unwanted pop-ups would require artificial intelligence in Privoxy. 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. Example usage: +kill-popups ------------------------------------------------------------------------------- 8.5.15. limit-connect Typical use: Prevent abuse of Privoxy as a TCP proxy relay 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. If you don't know what any of this means, there probably is no reason to change this one, since the default is already very restrictive. 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 (gaping security hole!) ------------------------------------------------------------------------------- 8.5.16. prevent-compression Typical use: Ensure that servers send the content uncompressed, so it can be passed through filters Effect: Adds a header to the request that asks for uncompressed 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): # Set default: # {+prevent-compression} / # Match all sites # Make exceptions for ill sites: # {-prevent-compression} www.debianhelp.org www.pclinuxonline.com ------------------------------------------------------------------------------- 8.5.17. 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 ------------------------------------------------------------------------------- 8.5.18. 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 ------------------------------------------------------------------------------- 8.5.19. 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. Example usage: +session-cookies-only ------------------------------------------------------------------------------- 8.5.20. 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). 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} ------------------------------------------------------------------------------- 8.5.21. 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. This is likely to change in future versions of Privoxy. 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: # +crunch-all-cookies = +crunch-incoming-cookies +crunch-outgoing-cookies -crunch-all-cookies = -crunch-incoming-cookies -crunch-outgoing-cookies +imageblock = +block +handle-as-image # These aliases define combinations of actions # that are useful for certain types of sites: # fragile = -block -crunch-all-cookies -filter -fast-redirects -hide-referer -kill-popups shop = -crunch-all-cookies -fast-redirects # Aliases defined from 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 .nytimes.com # Shopping sites: # Allow cookies (for setting and retrieving your customer data) # {shop} .quietpc.com .worldpay.com # for quietpc.com .scan.co.uk # These shops require pop-ups: # {shop -kill-popups -filter{popups}} .dabs.com .overclockers.co.uk Aliases like "shop" and "fragile" are often used for "problem" sites that require some actions to be disabled in order to function properly. ------------------------------------------------------------------------------- 8.7. Sample Actions Files Remember that the meaning of each action is reversed by preceding the action with a "-", in place of the "+". Also, that some actions are turned on in the default section of the actions file, and require little to no additional configuration. These are just "on". But, other actions that are turned on in the default section do typically require exceptions to be listed in the latter sections of one of our actions file. For instance, by default no URLs are "blocked" (i.e. in the default definitions of default.action). We need exceptions to this in order to enable ad blocking in the lower sections. But we need to be very selective about what we do block. Thus, the default is "off" for blocking. Below is a liberally commented sample default.action file to demonstrate how all the pieces come together. And to show how exceptions to the default policies can be handled. This is followed by a brief user.action with similar examples. # Sample default.action file # Settings -- Don't change! For internal Privoxy use ONLY. {{settings}} for-privoxy-version=3.0 ########################################################################## # Aliases must be defined *before* they are used. These are # easier to remember, and can combine several actions into one. Once # defined they can be used just like any built-in action -- but within # this file only! Aliases do not require a + or - sign. ########################################################################## {{alias}} # Some useful aliases. # Alias to turn off cookie handling, ie allow all cookies unmolested. # mercy-for-cookies = -crunch-incoming-cookies -crunch-outgoing-cookies \ -session-cookies-only # Alias to both block and treat as if an image for ad blocking # purposes. # +block-as-image = +block +handle-as-image # Shops should be allowed to set persistent cookies # shop = -filter mercy-for-cookies # Fragile sites should receive minimum interference: # fragile = -block -deanimate-gifs -fast-redirects -filter -hide-referer \ mercy-for-cookies -kill-popups ########################################################################## # Matching starts here. Remember that at this time, all actions are # disabled, so we need to explicitly enable the ones we want. # # We begin with "default" action settings, i.e. we define a set of actions # for a pattern ("/") that matches all URLs. This default set will be # applied to all requests as a start, and can be partly or wholly overridden # by later matches further down this file, or in user.action. # # We will show all potential actions here whether they are enabled # or not. We could omit any disabled action if we wanted, since all # actions are 'off' by default anyway. Shown for completeness only. # Actions are enabled if preceded by a '+', otherwise they are disabled # (unless an alias has been defined without this). ########################################################################## { \ -add-header \ -block \ -deanimate-gifs \ -downgrade-http-version \ +fast-redirects \ +filter{html-annoyances} \ +filter{js-annoyances} \ -filter{content-cookies} \ -filter{popups} \ +filter{webbugs} \ -filter{refresh-tags} \ -filter{fun} \ +filter{nimda} \ +filter{banners-by-size} \ -filter{shockwave-flash} \ -filter{crude-parental} \ +hide-forwarded-for-headers \ +hide-from-header{block} \ -hide-referrer \ -hide-user-agent \ -handle-as-image \ +set-image-blocker{pattern} \ -limit-connect \ +prevent-compression \ -session-cookies-only \ -crunch-outgoing-cookies \ -crunch-incoming-cookies \ -kill-popups \ -send-vanilla-wafer \ -send-wafer \ } / # forward slash will match *all* potential URL patterns. ########################################################################## # Default behavior is now set. Now we will define some exceptions to our # default action policies. ########################################################################## # These sites are very complex and require very minimal interference. # We'll disable most actions with our 'fragile' alias: { fragile } .office.microsoft.com # surprise, surprise! .windowsupdate.microsoft.com # Shopping sites - not as fragile but require some special # handling. We still want to block ads, and we will allow # persistent cookies via the 'shop' alias: { shop } .quietpc.com .worldpay.com # for quietpc.com .jungle.com .scan.co.uk # These sites require pop-ups too :( We'll combine our 'shop' # alias with two other actions into one rule to allow all popups. { shop -kill-popups -filter{popups} } .dabs.com .overclockers.co.uk # The 'Fast-redirects' action breaks some sites. Disable this action # for these known sensitive sites: { -fast-redirects } login.yahoo.com edit.europe.yahoo.com .google.com .altavista.com/.*(like|url|link):http .altavista.com/trans.*urltext=http .nytimes.com # Define which file types will be treated as images. Important # for ad blocking. { +handle-as-image } /.*\.(gif|jpe?g|png|bmp|ico) # Now lets list some domains that are known ad generators. And # our alias that we use here will block these as well as force # them to be treated as images. This combination of actions is # important for ad blocking. What the browser will show instead is # determined by the setting of "+set-image-blocker" { +imageblock } ar.atwola.com .ad.doubleclick.net .a.yimg.com/(?:(?!/i/).)*$ .a[0-9].yimg.com/(?:(?!/i/).)*$ bs*.gsanet.com bs*.einets.com .qkimg.net ad.*.doubleclick.net # These will just simply be blocked. They will generate the BLOCKED # banner page, if matched. Heavy use of wildcards and regular # expressions in this example. Enable block action: { +block } ad*. .*ads. banner?. count*. /.*count(er)?\.(pl|cgi|exe|dll|asp|php[34]?) /(?:.*/)?(publicite|werbung|rekla(ma|me|am)|annonse|maino(kset|nta|s)?)/ .hitbox.com # The above block section will probably inadvertently catch some # sites we DO NOT want blocked via the wildcards and regular expressions. # Now let's set exceptions to the exceptions so the good guys get better # treatment. Disable block action: { -block } advogato.org adsl. ad[ud]*. advice. # Let's just trust all .edu top level domains. .edu www.ugu.com/sui/ugu/adv # We'll need to access to path names containing 'download' .*downloads. /downloads/ # 'adv' is for globalintersec and means advanced, not advertisement www.globalintersec.com/adv # Don't filter *anything* from our friends at sourceforge. # Notice we don't have to name the individual filter # identifiers -- we just turn them all off in one fell swoop. # Disable all filters for this one site: { -filter } .sourceforge.net So far we are painting with a broad brush by setting general policies. The above would be a reasonable starting point for many situations. Now, we want to be more specific and have customized rules that are more suitable to our 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 should not be clobbered by upgrades. So any settings here, will have the last word and over-ride any previously defined actions. Now a few examples of some things that one might do with a user.action file. # Sample user.action file. # Any aliases you want to use need to be re-defined here. # Alias to turn off cookie handling, ie allow all cookies unmolested. -crunch-all-cookies = -crunch-incoming-cookies -crunch-outgoing-cookies \ -session-cookies-only # Fragile sites should have the minimum changes: fragile = -block -deanimate-gifs -fast-redirects -filter -hide-referer \ -crunch-all-cookies -kill-popups # Allow persistent cookies for a few regular sites that we # trust via our above alias. These will be saved from one browser session # to the next. We are explicitly turning off any and all cookie handling, # even though the crunch-*-cookies settings were disabled in our above # default.action anyway. So cookies from these domains will come through # unmolested. { -crunch-all-cookies } .sun.com .yahoo.com .msdn.microsoft.com .redhat.com # My ISP uses obnoxious self promoting images on many pages. # Nuke them :) Note that "+handle-as-image" need not be specified, # since all URLs ending in .gif will be tagged as images by the # general rules in default.action anyway. { +block } www.my-isp-example.com/logo[0-9].gif # Say the site where you do your home banking needs to open # popup windows, but you have chosen to kill popups by # default. This will allow it for your-example-bank.com: # { -filter{popups} -kill-popups } .my-example-bank.com # This site is delicate, and requires kid-glove # treatment. { fragile } .forbes.com ------------------------------------------------------------------------------- 9. The Filter File Any web page can be dynamically modified with the filter file. This modification can be removal, or re-writing, of any web page content, including tags and non-visible content. The default filter file is oddly enough default.filter, located in the config directory. This is potentially a very powerful feature, and requires knowledge of both "regular expression" and HTML in order create custom filters. But, there are a number of useful filters included with Privoxy for many common situations. The included example file is divided into sections. Each section begins with the FILTER keyword, followed by the identifier for that section, e.g. "FILTER: webbugs". Each section performs a similar type of filtering, such as "html-annoyances". This file uses regular expressions to alter or remove any string in the target page. The expressions can only operate on one line at a time. Some examples from the included default default.filter: Stop web pages from displaying annoying messages in the status bar by deleting such references: FILTER: html-annoyances # New browser windows should be resizeable and have a location and status # bar. Make it so. # s/resizable="?(no|0)"?/resizable=1/ig s/noresize/yesresize/ig s/location="?(no|0)"?/location=1/ig s/status="?(no|0)"?/status=1/ig s/scrolling="?(no|0|Auto)"?/scrolling=1/ig s/menubar="?(no|0)"?/menubar=1/ig # The tag was a crime! # s*|**ig # Is this evil? # #s/framespacing="?(no|0)"?//ig #s/margin(height|width)=[0-9]*//gi Just for kicks, replace any occurrence of "Microsoft" with "MicroSuck", and have a little fun with topical buzzwords: FILTER: fun s/microsoft(?!.com)/MicroSuck/ig # Buzzword Bingo: # s/industry-leading|cutting-edge|award-winning/BINGO!/ig Kill those pesky little web-bugs: # webbugs: Squish WebBugs (1x1 invisible GIFs used for user tracking) FILTER: webbugs s/]*?(width|height)\s*=\s*['"]?1\D[^>]*?(width|height)\s*=\s*['"]?1 (\D[^>]*?)?>//sig ------------------------------------------------------------------------------- 9.1. The +filter Action Filters are enabled with the "+filter" action from within one of the actions files. "+filter" requires one parameter, which should match one of the section identifiers in the filter file itself. Example: +filter{html-annoyances} This would activate that particular filter. Similarly, "+filter" can be turned off for selected sites as: "-filter{html-annoyances}". Remember too, all actions are off by default, unless they are explicitly enabled in one of the actions files. ------------------------------------------------------------------------------- 10. Templates When Privoxy displays one of its internal pages, such as a 404 Not Found error page (Privoxy must be running for link to work as intended), it uses the appropriate template. On Linux, BSD, and Unix, these are located in /etc/ privoxy/templates by default. These may be customized, if desired. cgi-style.css is used to control the HTML attributes (fonts, etc). The default Blocked (Privoxy needs to be running for page to display) banner page with the bright red top banner, is called just "blocked". This may be customized or replaced with something else if desired (not recommended for the casual user). ------------------------------------------------------------------------------- 11. Contacting the Developers, Bug Reporting and Feature Requests We value your feedback. However, to provide you with the best support, please note the following sections. ------------------------------------------------------------------------------- 11.1. Get Support To get support, use the Sourceforge Support Forum: http://sourceforge.net/tracker/?group_id=11118&atid=211118 ------------------------------------------------------------------------------- 11.2. Report bugs To submit bugs, use the Sourceforge Bug Forum: http://sourceforge.net/tracker/?group_id=11118&atid=111118. Make sure that the bug has not already been submitted. Please try to verify that it is a Privoxy bug, and not a browser or site bug first. If you are using your own custom configuration, please try the stock configs to see if the problem is a configuration related bug. And if not using the latest development snapshot, please try the latest one. Or even better, CVS sources. Please be sure to include the Privoxy version, platform, browser, any pertinent log data, any other relevant details (please be specific) and, if possible, some way to reproduce the bug. ------------------------------------------------------------------------------- 11.3. Request new features To submit ideas on new features, use the Sourceforge feature request forum: http://sourceforge.net/tracker/?atid=361118&group_id=11118&func=browse. ------------------------------------------------------------------------------- 11.4. Report ads or other filter problems You can also send feedback on websites that Privoxy has problems with. Please bookmark the following link: "Privoxy - Submit Filter Feedback". Once you surf to a page with problems, use the bookmark to send us feedback. We will look into the issue as soon as possible. New, improved default.action files will occasionally be made available based on your feedback. These will be announced on the ijbswa-announce list. ------------------------------------------------------------------------------- 11.5. Other For any other issues, feel free to use the mailing lists: http://sourceforge.net/mail/?group_id=11118. Anyone interested in actively participating in development and related discussions can also join the appropriate mailing list. Archives are available, too. See the page on Sourceforge. ------------------------------------------------------------------------------- 12. Privoxy Copyright, License and History Copyright © 2001, 2002 by Privoxy Developers Some source code is based on code Copyright © 1997 by Anonymous Coders and Junkbusters, Inc. and licensed under the GNU General Public License. ------------------------------------------------------------------------------- 12.1. License Privoxy is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License, version 2, as published by the Free Software Foundation. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details, which is available from the Free Software Foundation, Inc, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc. 59 Temple Place - Suite 330 Boston, MA 02111-1307 USA ------------------------------------------------------------------------------- 12.2. History Privoxy is evolved, and derived from, the Internet Junkbuster, with many improvements and enhancements over the original. Junkbuster was originally written by Anonymous Coders and Junkbusters Corporation, and was released as free open-source software under the GNU GPL. Stefan Waldherr made many improvements, and started the SourceForge project Privoxy to rekindle development. There are now several active developers contributing. The last stable release of Junkbuster was v2.0.2, which has now grown whiskers ;-). ------------------------------------------------------------------------------- 13. See Also Other references and sites of interest to Privoxy users: http://www.privoxy.org/, The Privoxy Home page. http://sourceforge.net/projects/ijbswa, the Project Page for Privoxy on Sourceforge. http://p.p/, access Privoxy from your browser. Alternately, http:// config.privoxy.org may work in some situations where the first does not. http://p.p/, and select "Privoxy - Submit Filter Feedback" to submit "misses" to the developers. http://www.junkbusters.com/ht/en/cookies.html http://www.waldherr.org/junkbuster/ http://privacy.net/analyze/ http://www.squid-cache.org/ ------------------------------------------------------------------------------- 14. Appendix 14.1. Regular Expressions Privoxy can use "regular expressions" in various config files. Assuming support for "pcre" (Perl Compatible Regular Expressions) is compiled in, which is the default. Such configuration directives do not require regular expressions, but they can be used to increase flexibility by matching a pattern with wild-cards against URLs. If you are reading this, you probably don't understand what "regular expressions" are, or what they can do. So this will be a very brief introduction only. A full explanation would require a book ;-) "Regular expressions" is a way of matching one character expression against another to see if it matches or not. One of the "expressions" is a literal string of readable characters (letter, numbers, etc), and the other is a complex string of literal characters combined with wild-cards, and other special characters, called meta-characters. The "meta-characters" have special meanings and are used to build the complex pattern to be matched against. Perl Compatible Regular Expressions is an enhanced form of the regular expression language with backward compatibility. To make a simple analogy, we do something similar when we use wild-card characters when listing files with the dir command in DOS. *.* matches all filenames. The "special" character here is the asterisk which matches any and all characters. We can be more specific and use ? to match just individual characters. So "dir file?.text" would match "file1.txt", "file2.txt", etc. We are pattern matching, using a similar technique to "regular expressions"! Regular expressions do essentially the same thing, but are much, much more powerful. There are many more "special characters" and ways of building complex patterns however. Let's look at a few of the common ones, and then some examples: . - Matches any single character, e.g. "a", "A", "4", ":", or "@". ? - The preceding character or expression is matched ZERO or ONE times. Either/ or. + - The preceding character or expression is matched ONE or MORE times. * - The preceding character or expression is matched ZERO or MORE times. \ - The "escape" character denotes that the following character should be taken literally. This is used where one of the special characters (e.g. ".") needs to be taken literally and not as a special meta-character. Example: "example \.com", makes sure the period is recognized only as a period (and not expanded to its meta-character meaning of any single character). [] - Characters enclosed in brackets will be matched if any of the enclosed characters are encountered. For instance, "[0-9]" matches any numeric digit (zero through nine). As an example, we can combine this with "+" to match any digit one of more times: "[0-9]+". () - parentheses are used to group a sub-expression, or multiple sub-expressions. | - The "bar" character works like an "or" conditional statement. A match is successful if the sub-expression on either side of "|" matches. As an example: "/(this|that) example/" uses grouping and the bar character and would match either "this example" or "that example", and nothing else. s/string1/string2/g - This is used to rewrite strings of text. "string1" is replaced by "string2" in this example. There must of course be a match on "string1" first. These are just some of the ones you are likely to use when matching URLs with Privoxy, and is a long way from a definitive list. This is enough to get us started with a few simple examples which may be more illuminating: /.*/banners/.* - A simple example that uses the common combination of "." and " *" to denote any character, zero or more times. In other words, any string at all. So we start with a literal forward slash, then our regular expression pattern (".*") another literal forward slash, the string "banners", another forward slash, and lastly another ".*". We are building a directory path here. This will match any file with the path that has a directory named "banners" in it. The ".*" matches any characters, and this could conceivably be more forward slashes, so it might expand into a much longer looking path. For example, this could match: "/eye/hate/spammers/banners/annoy_me_please.gif", or just "/ banners/annoying.html", or almost an infinite number of other possible combinations, just so it has "banners" in the path somewhere. A now something a little more complex: /.*/adv((er)?ts?|ertis(ing|ements?))?/ - We have several literal forward slashes again ("/"), so we are building another expression that is a file path statement. We have another ".*", so we are matching against any conceivable sub-path, just so it matches our expression. The only true literal that must match our pattern is adv, together with the forward slashes. What comes after the "adv" string is the interesting part. Remember the "?" means the preceding expression (either a literal character or anything grouped with "(...)" in this case) can exist or not, since this means either zero or one match. So "((er)?ts?|ertis(ing|ements?))" is optional, as are the individual sub-expressions: "(er)", "(ing|ements?)", and the "s". The " |" means "or". We have two of those. For instance, "(ing|ements?)", can expand to match either "ing" OR "ements?". What is being done here, is an attempt at matching as many variations of "advertisement", and similar, as possible. So this would expand to match just "adv", or "advert", or "adverts", or "advertising", or "advertisement", or "advertisements". You get the idea. But it would not match "advertizements" (with a "z"). We could fix that by changing our regular expression to: "/.*/adv((er)?ts?|erti(s|z)(ing|ements?))?/", which would then match either spelling. /.*/advert[0-9]+\.(gif|jpe?g) - Again another path statement with forward slashes. Anything in the square brackets "[]" can be matched. This is using "0-9" as a shorthand expression to mean any digit one through nine. It is the same as saying "0123456789". So any digit matches. The "+" means one or more of the preceding expression must be included. The preceding expression here is what is in the square brackets -- in this case, any digit one through nine. Then, at the end, we have a grouping: "(gif|jpe?g)". This includes a "|", so this needs to match the expression on either side of that bar character also. A simple "gif" on one side, and the other side will in turn match either "jpeg" or "jpg", since the "?" means the letter "e" is optional and can be matched once or not at all. So we are building an expression here to match image GIF or JPEG type image file. It must include the literal string "advert", then one or more digits, and a "." (which is now a literal, and not a special character, since it is escaped with "\"), and lastly either "gif", or "jpeg", or "jpg". Some possible matches would include: "//advert1.jpg", "/nasty/ads/ advert1234.gif", "/banners/from/hell/advert99.jpg". It would not match "advert1.gif" (no leading slash), or "/adverts232.jpg" (the expression does not include an "s"), or "/advert1.jsp" ("jsp" is not in the expression anywhere). s/microsoft(?!.com)/MicroSuck/i - This is a substitution. "MicroSuck" will replace any occurrence of "microsoft". The "i" at the end of the expression means ignore case. The "(?!.com)" means the match should fail if "microsoft" is followed by ".com". In other words, this acts like a "NOT" modifier. In case this is a hyperlink, we don't want to break it ;-). We are barely scratching the surface of regular expressions here so that you can understand the default Privoxy configuration files, and maybe use this knowledge to customize your own installation. There is much, much more that can be done with regular expressions. Now that you know enough to get started, you can learn more on your own :/ More reading on Perl Compatible Regular expressions: http://www.perldoc.com/ perl5.6/pod/perlre.html ------------------------------------------------------------------------------- 14.2. Privoxy's Internal Pages Since Privoxy proxies each requested web page, it is easy for Privoxy to trap certain special URLs. In this way, we can talk directly to Privoxy, and see how it is configured, see how our rules are being applied, change these rules and other configuration options, and even turn Privoxy's filtering off, all with a web browser. The URLs listed below are the special ones that allow direct access to Privoxy. Of course, Privoxy must be running to access these. If not, you will get a friendly error message. Internet access is not necessary either. * Privoxy main page: http://config.privoxy.org/ Alternately, this may be reached at http://p.p/, but this variation may not work as reliably as the above in some configurations. * Show information about the current configuration, including viewing and editing of actions files: http://config.privoxy.org/show-status * Show the source code version numbers: http://config.privoxy.org/show-version * Show the browser's request headers: http://config.privoxy.org/show-request * Show which actions apply to a URL and why: http://config.privoxy.org/show-url-info * Toggle Privoxy on or off. In this case, "Privoxy" continues to run, but only as a pass-through proxy, with no actions taking place: http://config.privoxy.org/toggle Short cuts. Turn off, then on: http://config.privoxy.org/toggle?set=disable http://config.privoxy.org/toggle?set=enable These may be bookmarked for quick reference. See next. ------------------------------------------------------------------------------- 14.2.1. Bookmarklets Below are some "bookmarklets" to allow you to easily access a "mini" version of some of Privoxy's special pages. They are designed for MS Internet Explorer, but should work equally well in Netscape, Mozilla, and other browsers which support JavaScript. They are designed to run directly from your bookmarks - not by clicking the links below (although that should work for testing). To save them, right-click the link and choose "Add to Favorites" (IE) or "Add Bookmark" (Netscape). You will get a warning that the bookmark "may not be safe" - just click OK. Then you can run the Bookmarklet directly from your favorites/bookmarks. For even faster access, you can put them on the "Links" bar (IE) or the "Personal Toolbar" (Netscape), and run them with a single click. * Privoxy - Enable * Privoxy - Disable * Privoxy - Toggle Privoxy (Toggles between enabled and disabled) * Privoxy- View Status * Privoxy - Submit Filter Feedback Credit: The site which gave me the general idea for these bookmarklets is www.bookmarklets.com. They have more information about bookmarklets. ------------------------------------------------------------------------------- 14.3. Chain of Events Let's take a quick look at the basic sequence of events when a web page is requested by your browser and Privoxy is on duty: * First, your web browser requests a web page. The browser knows to send the request to Privoxy, which will in turn, relay the request to the remote web server after passing the following tests: * Privoxy traps any request for its own internal CGI pages (e.g http://p.p/) and sends the CGI page back to the browser. * Next, Privoxy checks to see if the URL matches any "+block" patterns. If so, the URL is then blocked, and the remote web server will not be contacted. "+handle-as-image" is then checked and if it does not match, an HTML "BLOCKED" page is sent back. Otherwise, if it does match, an image is returned. The type of image depends on the setting of "+set-image-blocker" (blank, checkerboard pattern, or an HTTP redirect to an image elsewhere). * Untrusted URLs are blocked. If URLs are being added to the trust file, then that is done. * If the URL pattern matches the "+fast-redirects" action, it is then processed. Unwanted parts of the requested URL are stripped. * Now the rest of the client browser's request headers are processed. If any of these match any of the relevant actions (e.g. "+hide-user-agent", etc.), headers are suppressed or forged as determined by these actions and their parameters. * Now the web server starts sending its response back (i.e. typically a web page and related data). * First, the server headers are read and processed to determine, among other things, the MIME type (document type) and encoding. The headers are then filtered as determined by the "+crunch-incoming-cookies", "+session-cookies-only", and "+downgrade-http-version" actions. * If the "+kill-popups" action applies, and it is an HTML or JavaScript document, the popup-code in the response is filtered on-the-fly as it is received. * If a "+filter" or "+deanimate-gifs" action applies (and the document type fits the action), the rest of the page is read into memory (up to a configurable limit). Then the filter rules (from default.filter) are processed against the buffered content. Filters are applied in the order they are specified in the default.filter file. Animated GIFs, if present, are reduced to either the first or last frame, depending on the action setting.The entire page, which is now filtered, is then sent by Privoxy back to your browser. If neither "+filter" or "+deanimate-gifs" matches, then Privoxy passes the raw data through to the client browser as it becomes available. * As the browser receives the now (probably filtered) page content, it reads and then requests any URLs that may be embedded within the page source, e.g. ad images, stylesheets, JavaScript, other HTML documents (e.g. frames), sounds, etc. For each of these objects, the browser issues a new request. And each such request is in turn processed as above. Note that a complex web page may have many such embedded URLs. ------------------------------------------------------------------------------- 14.4. Anatomy of an Action The way Privoxy applies "actions" and "filters" to any given URL can be complex, and not always so easy to understand what is happening. And sometimes we need to be able to see just what Privoxy is doing. Especially, if something Privoxy is doing is causing us a problem inadvertently. It can be a little daunting to look at the actions and filters files themselves, since they tend to be filled with "regular expressions" whose consequences are not always so obvious. One quick test to see if Privoxy is causing a problem or not, is to disable it temporarily. This should be the first troubleshooting step. See the Bookmarklets section on a quick and easy way to do this (be sure to flush caches afterward!). Privoxy also provides the http://config.privoxy.org/show-url-info page that can show us very specifically how actions are being applied to any given URL. This is a big help for troubleshooting. First, enter one URL (or partial URL) at the prompt, and then Privoxy will tell us how the current configuration will handle it. This will not help with filtering effects (i.e. the "+filter" action) from the default.filter file since this is handled very differently and not so easy to trap! It also will not tell you about any other URLs that may be embedded within the URL you are testing. For instance, images such as ads are expressed as URLs within the raw page source of HTML pages. So you will only get info for the actual URL that is pasted into the prompt area -- not any sub-URLs. If you want to know about embedded URLs like ads, you will have to dig those out of the HTML source. Use your browser's "View Page Source" option for this. Or right click on the ad, and grab the URL. Let's try an example, google.com, and look at it one section at a time: Matches for http://google.com: --- File standard --- (no matches in this file) --- File default --- { -add-header -block +deanimate-gifs{last} -downgrade-http-version +fast-redirects -filter{popups} -filter{fun} -filter{shockwave-flash} -filter{crude-parental} +filter{html-annoyances} +filter{js-annoyances} +filter{content-cookies} +filter{webbugs} +filter{refresh-tags} +filter{nimda} +filter{banners-by-size} +hide-forwarded-for-headers +hide-from-header{block} +hide-referer{forge} -hide-user-agent -handle-as-image +set-image-blocker{pattern} -limit-connect +prevent-compression +session-cookies-only -crunch-outgoing-cookies -crunch-incoming-cookies -kill-popups -send-vanilla-wafer -send-wafer } / { -session-cookies-only } .google.com { -fast-redirects } .google.com --- File user --- (no matches in this file) This tells us how we have defined our "actions", and which ones match for our example, "google.com". The first listing is any matches for the standard.action file. No hits at all here on "standard". Then next is "default", or our default.action file. The large, multi-line listing, is how the actions are set to match for all URLs, i.e. our default settings. If you look at your "actions" file, this would be the section just below the "aliases" section near the top. This will apply to all URLs as signified by the single forward slash at the end of the listing -- "/". But we can define additional actions that would be exceptions to these general rules, and then list specific URLs (or patterns) that these exceptions would apply to. Last match wins. Just below this then are two explicit matches for ".google.com". The first is negating our previous cookie setting, which was for "+session-cookies-only" (i.e. not persistent). So we will allow persistent cookies for google. The second turns off any "+fast-redirects" action, allowing this to take place unmolested. Note that there is a leading dot here -- ".google.com". This will match any hosts and sub-domains, in the google.com domain also, such as "www.google.com". So, apparently, we have these two actions defined somewhere in the lower part of our default.action file, and "google.com" is referenced somewhere in these latter sections. Then, for our user.action file, we again have no hits. And finally we pull it all together in the bottom section and summarize how Privoxy is applying all its "actions" to "google.com": Final results: -add-header -block +deanimate-gifs{last} -downgrade-http-version -fast-redirects -filter{popups} -filter{fun} -filter{shockwave-flash} -filter{crude-parental} +filter{html-annoyances} +filter{js-annoyances} +filter{content-cookies} +filter{webbugs} +filter{refresh-tags} +filter{nimda} +filter{banners-by-size} +hide-forwarded-for-headers +hide-from-header{block} +hide-referer{forge} -hide-user-agent -handle-as-image +set-image-blocker{pattern} -limit-connect +prevent-compression -session-cookies-only -crunch-outgoing-cookies -crunch-incoming-cookies -kill-popups -send-vanilla-wafer -send-wafer Notice the only difference here to the previous listing, is to "fast-redirects" and "session-cookies-only". Now another example, "ad.doubleclick.net": { +block +handle-as-image } .ad.doubleclick.net { +block +handle-as-image } ad*. { +block +handle-as-image } .doubleclick.net We'll just show the interesting part here, the explicit matches. It is matched three different times. Each as an "+block +handle-as-image", which is the expanded form of one of our aliases that had been defined as: "+imageblock". ( "Aliases" are defined in the first section of the actions file and typically used to combine more than one action.) Any one of these would have done the trick and blocked this as an unwanted image. This is unnecessarily redundant since the last case effectively would also cover the first. No point in taking chances with these guys though ;-) Note that if you want an ad or obnoxious URL to be invisible, it should be defined as "ad.doubleclick.net" is done here -- as both a "+block" and an "+handle-as-image". The custom alias "+imageblock" just simplifies the process and make it more readable. One last example. Let's try "http://www.rhapsodyk.net/adsl/HOWTO/". This one is giving us problems. We are getting a blank page. Hmmm... Matches for http://www.rhapsodyk.net/adsl/HOWTO/: { -add-header -block +deanimate-gifs -downgrade-http-version +fast-redirects +filter{html-annoyances} +filter{js-annoyances} +filter{kill-popups} +filter{webbugs} +filter{nimda} +filter{banners-by-size} +filter{hal} +filter{fun} +hide-forwarded-for-headers +hide-from-header{block} +hide-referer{forge} -hide-user-agent -handle-as-image +set-image-blocker{blank} +prevent-compression +session-cookies-only -crunch-incoming-cookies -crunch-outgoing-cookies +kill-popups -send-vanilla-wafer -send-wafer } / { +block +handle-as-image } /ads Ooops, the "/adsl/" is matching "/ads"! But we did not want this at all! Now we see why we get the blank page. We could now add a new action below this that explicitly does not block ("{-block}") paths with "adsl". There are various ways to handle such exceptions. Example: { -block } /adsl Now the page displays ;-) Be sure to flush your browser's caches when making such changes. Or, try using Shift+Reload. But now what about a situation where we get no explicit matches like we did with: { +block +handle-as-image } /ads That actually was very telling and pointed us quickly to where the problem was. If you don't get this kind of match, then it means one of the default rules in the first section is causing the problem. This would require some guesswork, and maybe a little trial and error to isolate the offending rule. One likely cause would be one of the "{+filter}" actions. Try adding the URL for the site to one of aliases that turn off "+filter": {shop} .quietpc.com .worldpay.com # for quietpc.com .jungle.com .scan.co.uk .forbes.com "{shop}" is an "alias" that expands to "{ -filter -session-cookies-only }". Or you could do your own exception to negate filtering: {-filter} .forbes.com This would probably be most appropriately put in user.action, for local site exceptions. "{fragile}" is an alias that disables most actions. This can be used as a last resort for problem sites. Remember to flush caches! If this still does not work, you will have to go through the remaining actions one by one to find which one(s) is causing the problem.