updated files from SGML code.

[privoxy.git] / doc / text / user-manual.txt

Junkbuster User Manual

   By: Junkbuster Developers
   
   $Id: user-manual.sgml,v 1.20 2001/10/24 23:58:25 hal9 Exp $
   
   The user manual gives the users information on how to install and
   configure Internet Junkbuster. Internet Junkbuster is an application
   that provides privacy and security to users of the World Wide Web.
   
   You can find the latest version of the user manual at
   [1]http://ijbswa.sourceforge.net/user-manual/.
   
   Feel free to send a note to the developers at
   <[2]ijbswa-developers@lists.sourceforge.net>.
     _________________________________________________________________
   
   Table of Contents
   1. [3]Introduction
          
        1.1. [4]New Features
                
   2. [5]Installation
          
        2.1. [6]Source
        2.2. [7]Red Hat
        2.3. [8]SuSE
        2.4. [9]OS/2
        2.5. [10]Windows
        2.6. [11]Other
                
   3. [12]Junkbuster Configuration
          
        3.1. [13]The Main Configuration File
        3.2. [14]The Actions File
        3.3. [15]The Filter File
                
   4. [16]Quickstart to Using Junkbuster
   5. [17]Contact the Developers
   6. [18]Copyright and History
          
        6.1. [19]License
        6.2. [20]History
                
   7. [21]See also
   8. [22]Appendix
          
        8.1. [23]Regular Expressions
                
1. Introduction

   Internet Junkbuster 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. Junkbuster has a very
   flexible configuration and can be customized to suit individual needs
   and tastes. Internet Junkbuster has application for both stand-alone
   systems and multi-user networks.
   
   This documentation is included with the current development version of
   Internet Junkbuster and is incomplete 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 underway, and includes many significant
   changes and enhancements over earlier verions. The target release date
   for stable v3.0 is December 2001.
   
   Since this is a development version, some features are in the process
   of being implemented. This documentation may be slightly out of sync
   as a result. And there are bugs, though hopefully not many!
     _________________________________________________________________
   
1.1. New Features

   In addition to Junkbuster's traditional features of ad and banner
   blocking and cookie management, this is a list of new features
   currently under development:
   
     * A browser based configuration utility (WIP at [24]http://i.j.b).
     * Modularized configuration that will allow for system wide
       settings, and individual user settings. (not implemented yet)
     * Blocking of annoying pop-up browser windows (previously available
       as a patch).
     * Support for HTTP/1.1 (partially implemented at this point).
     * Support for Perl Compatible Regular Expressions in the
       configuration files, and generally a more sophisticated
       configuration syntax over previous versions.
     * Web page content filtering.
     * Multi-threaded.
       
   In addition, the configuration is more versatile overall.
     _________________________________________________________________
   
2. Installation

   Junkbuster is available as raw source code, or pre-compiled binaries.
   See the [25]Junkbuster Home Page for current release info. Junkbuster
   is also available via [26]CVS. This is the recommended approach at
   this time. But please be aware that CVS is constantly changing, and it
   may break in mysterious ways.
     _________________________________________________________________
   
2.1. Source

   For gzipped tar archives, unpack the source:
   
 tar zxvf ijb_source_2.9*
 cd ijb_source_2.9*

   For retrieving the current CVS sources, you'll need the CVS package
   installed first. 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 cu
rrent
  cd current

   This will create a directory named current/, which will contain the
   source tree.
   
   Then, in either case, to build from source:
   
 autoconf           #recommended for CVS source
 ./configure
 make
 su
 make install

   For Redhat and SuSE Linux RPM packages, see below.
     _________________________________________________________________
   
2.2. Red Hat

   To build Redhat RPM packages, install source as above. Then:
   
 autoconf              #recommended for CVS source
 ./configure
 make redhat-dist

   This will create both binary and src RPMs in the usual places.
   Example:
   
      /usr/src/redhat/RPMS/i686/junkbuster-2.9.8-1.i686.rpm
   
      /usr/src/redhat/SRPMS/junkbuster-2.9.9-1.src.rpm
   
   To install, of course:
   
 rpm -Uvv /usr/src/redhat/RPMS/i686/junkbuster-2.9.9-1.i686.rpm

   This will place the Junkbuster configuration files in
   /etc/junkbuster/, and log files in /var/log/junkbuster/.
     _________________________________________________________________
   
2.3. SuSE

   To build SuSE RPM packages, install source as above. Then:
   
 autoconf             #recommended for CVS source
 ./configure
 make suse-dist

   This will create both binary and src RPMs in the usual places.
   Example:
   
      /usr/src/suse/RPMS/i686/junkbuster-2.9.9-1.i686.rpm
   
      /usr/src/suse/SRPMS/junkbuster-2.9.9-1.src.rpm
   
   To install, of course:
   
 rpm -Uvv /usr/src/suse/RPMS/i686/junkbuster-2.9.9-1.i686.rpm

   This will place the Junkbuster configuration files in
   /etc/junkbuster/, and log files in /var/log/junkbuster/.
     _________________________________________________________________
   
2.4. OS/2

   The OS/2 version of Junkbuster requires the EMX runtime library to be
   installed. The EMX runtime library is available on the hobbes OS/2
   archive, among many other locations:
   [27]http://hobbes.nmsu.edu/cgi-bin/h-search?sh=1&button=Search&key=emx
   rt.zip&stype=all&sort=type&dir=%2Fpub%2Fos2%2Fdev%2Femx%2Fv0.9d
   
   Junkbuster is packaged in a WarpIN self- installing archive. The
   self-installing program will be named depending on the release
   version, something like: ijbos123.exe. In order to install it, simply
   run this executable or double-click on its icon and follow the WarpIN
   installation panels. A shadow of the Junkbuster executable will be
   placed in your startup folder so it will start automatically whenever
   OS/2 starts.
   
   The directory you choose to install Junkbuster into will contain all
   of the configuration files.
   
   If you would like to build binary images on OS/2 yourself, you will
   need a working EMX/GCC environment, plus several Unix-like tools. The
   Hobbes OS/2 archive is a good place to start when building such an
   environment. A set of Unix-like tools named gnupack is located here:
   [28]http://hobbes.nmsu.edu/cgi-bin/h-search?sh=1&key=gnupack&stype=all
   &sort=type&dir=%2Fpub%2Fos2%2Fapps
   
   Once you have the source code unpacked as above, you can build the
   binaries from the current/ directory:
   
 autoconf
 sh configure
 make
     _________________________________________________________________
   
2.5. Windows

   Click-click. (I need help on this. Not a clue here. Also for
   configuration section below. HB.)
     _________________________________________________________________
   
2.6. Other

   Some quick notes on other Operating Systems.
   
   For FreeBSD (and other *BSDs?), the build will need gmake instead of
   the included make. gmake is available from [29]http://www.gnu.org. The
   rest should be the same as above for Linux/Unix.
     _________________________________________________________________
   
3. Junkbuster Configuration

   For Unix, *BSD and Linux, all configuraton files are located in
   /etc/junkbuster/ by default. For MS Windows and OS/2, these are all in
   the same directory as the Junkbuster 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. For the
   time being, there are only three default configuration files (this
   will change in time):
   
     * The main configuration file is named config on Linux, Unix, BSD,
       and OS/2, and junkbustr.txt on Windows. On Amiga, it is
       AmiTCP:db/junkbuster/config.
     * The actionsfile file is used to define various "actions" relating
       to images, banners, pop-ups, access restrictions, banners and
       cookies. There is a CGI based editor for this file that can be
       accessed via [30]http://i.j.b./. This is the easiest method of
       configuring actions. (Still under active development.)
     * The re_filterfile file can be used to rewrite the raw page
       content, including text as well as embedded HTML and JavaScript.
       
   actionsfile and re_filterfile can use Perl style regular expressions
   for maximum flexibility. All files use the "#" character to denote a
   comment. Such lines are not processed by Junkbuster. After making any
   changes, restart Junkbuster in order for the changes to take effect.
   
   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.
     _________________________________________________________________
   
3.1. The Main Configuration File

   Again, the main configuration file is named config on Linux/Unix/BSD
   and OS/2, and junkbustr.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:
   
     blockfile blocklist.ini
   
   Indicates that the blockfile is named "blocklist.ini".
   
   A "#" indicates a comment. Any part of a line following a "#" is
   ignored, except if the "#" is preceded by a "\".
   
   Thus, by placing a "#" at the start of an existing configuration line,
   you can make it a comment and it will be treated as if it weren't
   there. This is called "commenting out" an option and can be useful to
   turn off features: If you comment out the "logfile" line, junkbuster
   will not log to a file at all. Watch for the "default:" section in
   each explanation to see what happens if the option is left unset (or
   commented out).
   
   Long lines can be continued on the next line by using a "\" as the
   very last character.
   
   There are various aspects of Junkbuster behavior that can be tuned.
     _________________________________________________________________
   
3.1.1. Defining Other Configuration Files

   Junkbuster can use a number of other files to tell it what ads to
   block, what cookies to accept, etc. This section of the configuration
   file tells Junkbuster where to find all those other files.
   
   On Windows, Junkbuster looks for these files in the same directory as
   the executable. On Unix and OS/2, Junkbuster looks for these files in
   the current working directory. In either case, an absolute path name
   can be used to avoid problems.
   
   When development goes modular and multiuser, the blocker, filter, and
   per-user config will be stored in subdirectories of "confdir". For
   now, only confdir/templates is used for storing HTML templates for CGI
   results.
   
   The location of the configuration files:
   
     confdir /etc/junkbuster       # No trailing /, please.
   
   The directory where all logging (i.e. logfile and jarfile) takes
   place. No trailing "/", please:
   
     logdir /var/log/junkbuster
   
   Note that all file specifications below are relative to the above two
   directories!
   
   The "actionsfile" contains patterns to specify the actions to apply to
   requests for each site. Default: Cookies to and from all destinations
   are filtered. Popups are disabled for all sites. All sites are
   filtered if re_filterfile specified. No sites are blocked. An empty
   image is displayed for filtered ads and other images (formerly
   "tinygif"). The syntax of this file is explained in detail [31]below.
   
     actionsfile actionsfile
   
   The "re_filterfile" file contains content modification rules. These
   rules permit powerful changes on the content of Web pages, e.g., you
   could disable your favourite JavaScript annoyances, rewrite the actual
   content, or just have some fun replacing "Microsoft" with "MicroSuck"
   wherever it appears on a Web page. Default: No content modification,
   or whatever the developers are playing with :-/
   
     re_filterfile re_filterfile
   
   The logfile is where all logging and error messages are written. The
   logfile can be useful for tracking down a problem with Junkbuster
   (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 Redhat, a logrotate script has been
   included.
   
   On SuSE Linux systems, you can place a line like
   "/var/log/junkbuster.* +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.
   
   Default: Log to the a file named logfile. Comment out to disable
   logging.
   
     logfile logfile
   
   The "jarfile" defines where Junkbuster stores the cookies it
   intercepts. Note that if you use a "jarfile", it may grow quite large.
   Default: Don't store intercepted cookies.
   
     #jarfile jarfile
   
   If you specify a "trustfile", Junkbuster will only allow access to
   sites that are named in the trustfile. You can also mark sites as
   trusted referrers, 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". This is a very
   restrictive feature that typical users most propably want to leave
   disabled. Default: Disabled, don't use the trust mechanism.
   
     #trustfile trust
   
   If you use the trust mechanism, it is a good idea to write up some
   online documentation about your blocking policy and to specify the
   URL(s) here. They will appear on the page that your users receive when
   they try to access untrusted content. Use multiple times for multiple
   URLs. Default: Don't display links on the "untrusted" info page.
   
     trust-info-url http://www.your-site.com/why_we_block.html
     trust-info-url http://www.your-site.com/what_we_allow.html
     _________________________________________________________________
   
3.1.2. Other Configuration Options

   This part of the configuration file contains options that control how
   Junkbuster operates.
   
   "Admin-address" should be set to the email address of the proxy
   administrator. It is used in many of the proxy-generated pages.
   Default: fill@me.in.please.
   
     #admin-address fill@me.in.please
   
   "Proxy-info-url" can be set to a URL that contains more info about
   this Junkbuster installation, it's configuration and policies. It is
   used in many of the proxy-generated pages and its use is highly
   recommended in multi-user installations, since your users will want to
   know why certain content is blocked or modified. Default: Don't show a
   link to online documentation.
   
     proxy-info-url http://www.your-site.com/proxy.html
   
   "Listen-address" specifies the address and port where Junkbuster will
   listen for connections from your Web browser. The default is to listen
   on the localhost port 8000, and this is suitable for most users. (In
   your web browser, under proxy configuration, list the proxy server as
   "localhost" and the port as "8000").
   
   If you already have another service running on port 8000, 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. The syntax is
   "listen-address [<ip-address>]:<port>". If you leave out the IP
   address, junkbuster 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 "aclfile" above), or
   a firewall.
   
   For example, suppose you are running Junkbuster 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 192.168.0.1:8000
   
   If you want it to listen on all addresses (including the outside
   connection):
   
     listen-address :8000
   
   If you do this, consider using ACLs (see "aclfile" above). Note: you
   will need to point your browser(s) to the address and port that you
   have configured here. Default: localhost:8000 (127.0.0.1:8000).
   
   The debug option sets the level of debugging information to log in the
   logfile (and to the console in the Windows version). A debug level of
   1 is informative because it will show you each request as it happens.
   Higher levels of debug are probably only of interest to developers.
   
     debug         1 # GPC   = show each GET/POST/CONNECT request
     debug         2 # CONN  = show each connection status
     debug         4 # IO    = show I/O status
     debug         8 # HDR   = show header parsing
     debug        16 # LOG   = log all data into the logfile
     debug        32 # FRC   = debug force feature
     debug        64 # REF   = debug regular expression filter
     debug       128 #       = debug fast redirects
     debug       256 #       = debug GIF deanimation
     debug       512 # CLF   = Common Log Format
     debug      1024 #       = debug kill popups
     debug      4096 # INFO  = Startup banner and warnings.
     debug      8192 # ERROR = Non-fatal errors
   
   It is highly recommended that you enable ERROR reporting (debug 8192),
   at least until the next stable release.
   
   The reporting of FATAL errors (i.e. ones which crash JunkBuster) is
   always on and cannot be disabled.
   
   If you want to use CLF (Common Log Format), you should set "debug 512"
   ONLY, do not enable anything else.
   
   Multiple "debug" directives, are OK - they're logical-OR'd together.
   
     debug 15 # same as setting the first 4 listed above
   
   Default:
   
     debug 1 # URLs
     debug 4096 # Info
     debug 8192 # Errors - *we highly recommended enabling this*
   
   Junkbuster normally uses "multi-threading", a software technique that
   permits it to handle many different requests simultaneously. In some
   cases you may wish to disable this -- particularly if you're trying to
   debug a problem. The "single-threaded" option forces Junkbuster to
   handle requests sequentially. Default: Multi-threaded mode.
   
     #single-threaded
   
   "toggle" allows you to temporarily disable all Junkbuster's filtering.
   Just set "toggle 0".
   
   The Windows version of Junkbuster puts an icon in the system tray,
   which also allows you to change this option. If you right-click on
   that icon (or select the "Options" menu), one choice is "Enable".
   Clicking on enable toggles Junkbuster on and off. This is useful if
   you want to temporarily disable Junkbuster, e.g., to access a site
   that requires cookies which you normally have blocked. This can also
   be toggled via a web browser at the Junkbuster internal address of
   [32]http://i.j.b./ on any platform.
   
   "toggle 1" means Junkbuster runs normally, "toggle 0" means that
   Junkbuster becomes a non-anonymizing non-blocking proxy. Default: 1
   (on).
   
     toggle 1
   
   For content filtering, i.e. the "+filter" and "+deanimate-gif"
   actions, it is neccessary that Junkbuster 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.
   
   The buffer-limit option lets you set the maximum size in Kbytes that
   each buffer may use. When the documents buffer exceeds this size, it
   is flushed to the client unfiltered and no further attempt to filter
   the rest of it is made. Remember that there may multiple threads
   running, which might require increasing the "buffer-limit" Kbytes
   each, unless you have enabled "single-threaded" above.
   
     buffer-limit 4069
   
   To enable the web-based actionsfile editor set enable-edit-actions to
   1, or 0 to disable. Note that you must have compiled JunkBuster with
   support for this feature, otherwise this option has no effect. This
   internal page can be reached at [33]http://i.j.b./.
   
   Security note: If this is enabled, anyone who can use the proxy can
   edit the actions file, and their changes will affect all users. For
   shared proxies, you probably want to disable this. Default: enabled.
   
     enable-edit-actions 1
   
   Allow JunkBuster to be toggled on and off remotely, using your web
   browser. Set "enable-remote-toggle"to 1 to enable, and 0 to disable.
   Note that you must have compiled JunkBuster with support for this
   feature, otherwise this option has no effect.
   
   Security note: If this is enabled, anyone who can use the proxy can
   toggle it on or off (see [34]http://i.j.b./), and their changes will
   affect all users. For shared proxies, you probably want to disable
   this. Default: enabled.
   
     enable-remote-toggle 1
     _________________________________________________________________
   
3.1.3. Access Control List (ACL)

   Access controls are included at the request of some ISPs and systems
   administrators, and are not usually needed by individual users. Please
   note 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.
   
   If no access settings are specified, the proxy talks to anyone that
   connects. If any access settings file are specified, then the proxy
   talks only to IP addresses permitted somewhere in this file and not
   denied later in this file.
   
   Summary -- if using an ACL:
   
   Client must have permission to receive service.
   
   LAST match in ACL wins.
   
   Default behavior is to deny service.
   
   The syntax for an entry in the Access Control List is:
   
     ACTION    SRC_ADDR[/SRC_MASKLEN]    [ DST_ADDR[/DST_MASKLEN] ]
   
   Where the individual fields are:
   
    ACTION      = "permit-access" or "deny-access"
    SRC_ADDR    = client hostname or dotted IP address
    SRC_MASKLEN = number of bits in the subnet mask for the source
    DST_ADDR    = server or forwarder hostname or dotted IP address
    DST_MASKLEN = number of bits in the subnet mask for the target
   
   The field separator (FS) is whitespace (space or tab).
   
   IMPORTANT NOTE: If the junkbuster is using a forwarder (see below) or
   a gateway for a particular destination URL, the DST_ADDR that is
   examined is the address of the forwarder or the gateway and NOT the
   address of the ultimate target. This is necessary because it may be
   impossible for the local Junkbuster to determine the address of the
   ultimate target (that's often what gateways are used for).
   
   Here are a few examples to show how the ACL features work:
   
   "localhost" is OK -- no DST_ADDR implies that ALL destination
   addresses are OK:
   
     permit-access localhost
   
   A silly example to illustrate permitting any host on the class-C
   subnet with Junkbuster to go anywhere:
   
     permit-access www.junkbusters.com/24
   
   Except deny one particular IP address from using it at all:
   
     deny-access ident.junkbusters.com
   
   You can also specify an explicit network address and subnet mask.
   Explicit addresses do not have to be resolved to be used.
   
     permit-access 207.153.200.0/24
   
   A subnet mask of 0 matches anything, so the next line permits
   everyone.
   
     permit-access 0.0.0.0/0
   
   Note, you cannot say:
   
     permit-access .org
   
   to allow all *.org domains. Every IP address listed must resolve
   fully.
   
   An ISP may want to provide a Junkbuster that is accessible by "the
   world" and yet restrict use of some of their private content to hosts
   on its internal network (i.e. its own subscribers). Say, for instance
   the ISP owns the Class-B IP address block 123.124.0.0 (a 16 bit
   netmask). This is how they could do it:
   
    permit-access 0.0.0.0/0 0.0.0.0/0   # other clients can go anywhere
                                          # with the following exceptions
   :
   
    deny-access   0.0.0.0/0   123.124.0.0/16 # block all external request
   s for
                                             # sites on the ISP's network
    permit 0.0.0.0/0 www.my_isp.com        # except for the ISP's main
                                             # web site
    permit 123.124.0.0/16 0.0.0.0/0          # the ISP's clients can go
                                             # anywhere
   
   Note that if some hostnames are listed with multiple IP addresses, the
   primary value returned by DNS (via gethostbyname()) is used. Default:
   Anyone can access the proxy.
     _________________________________________________________________
   
3.1.4. Forwarding

   This feature allows chaining of HTTP requests via multiple proxies. It
   can be used to better protect privacy and confidentiality when
   accessing specific domains by routing requests to those domains to a
   special purpose filtering proxy such as lpwa.com. Or to use a caching
   proxy to speed up browsing.
   
   It can also be used in an environment with multiple networks to route
   requests via multiple gateways allowing transparent access to multiple
   networks without having to modify browser configurations.
   
   Also specified here are SOCKS proxies. Junkbuster SOCKS 4 and SOCKS
   4A. The difference is that SOCKS 4A will resolve the target hostname
   using DNS on the SOCKS server, not our local DNS client.
   
   The syntax of each line is:
   
    forward target_domain[:port] http_proxy_host[:port]
    forward-socks4 target_domain[:port] socks_proxy_host[:port]
   http_proxy_host[:port]
    forward-socks4a target_domain[:port] socks_proxy_host[:port]
   http_proxy_host[:port]
   
   If http_proxy_host is ".", then requests are not forwarded to a HTTP
   proxy but are made directly to the web servers.
   
   Lines are checked in sequence, and the last match wins.
   
   There is an implicit line equivalent to the following, which specifies
   that anything not finding a match on the list is to go out without
   forwarding or gateway protocol, like so:
   
     forward .* . # implicit
   
   In the following common configuration, everything goes to Lucent's
   LPWA, except SSL on port 443 (which it doesn't handle):
   
    forward .* lpwa.com:8000
    forward :443 .
   
   See the FAQ for instructions on how to automate the login procedure
   for LPWA. Some users have reported difficulties related to LPWA's use
   of "." as the last element of the domain, and have said that this can
   be fixed with this:
   
     forward lpwa. lpwa.com:8000
   
   (NOTE: the syntax for specifiying target_domain has changed since the
   previous paragraph was written -- it will not work now. More
   information is welcome.)
   
   In this fictitious example, everything goes via an ISP's caching
   proxy, except requests to that ISP:
   
    forward .* caching.myisp.net:8000
    forward myisp.net .
   
   For the @home network, we're told the forwarding configuration is
   this:
   
     forward .* proxy:8080
   
   Also, we're told they insist on getting cookies and JavaScript, so you
   need to add home.com to the cookie file. We consider JavaScript a
   security risk. Java need not be enabled.
   
   In this example direct connections are made to all "internal" domains,
   but everything else goes through Lucent's LPWA by way of the company's
   SOCKS gateway to the Internet.
   
    forward_socks4 .* lpwa.com:8000 firewall.my_company.com:1080
    forward my_company.com .
   
   This is how you could set up a site that always uses SOCKS but no
   forwarders:
   
     forward_socks4a .* . firewall.my_company.com:1080
   
   An advanced example for network administrators:
   
   If you have links to multiple ISPs that provide various special
   content to their subscribers, you can configure forwarding to pass
   requests to the specific host that's connected to that ISP so that
   everybody can see all of the content on all of the ISPs.
   
   This is a bit tricky, but here's an example:
   
   host-a has a PPP connection to isp-a.com. And host-b has a PPP
   connection to isp-b.com. host-a can run a Junkbuster proxy with
   forwarding like this:
   
    forward .* .
    forward isp-b.com host-b:8000
   
   host-b can run a Junkbuster proxy with forwarding like this:
   
    forward .* .
    forward isp-a.com host-a:8000
   
   Now, anyone on the Internet (including users on host-a and host-b) can
   set their browser's proxy to either host-a or host-b and be able to
   browse the content on isp-a or isp-b.
   
   Here's another practical example, for University of Kent at Canterbury
   students with a network connection in their room, who need to use the
   University's Squid web cache.
   
    forward *. ssbcache.ukc.ac.uk:3128  # Use the proxy, except for:
    forward .ukc.ac.uk .  # Anything on the same domain as us
    forward * .  # Host with no domain specified
    forward 129.12.*.* .  # A dotted IP on our /16 network.
    forward 127.*.*.* .  # Loopback address
    forward localhost.localdomain .  # Loopback address
    forward www.ukc.mirror.ac.uk .  # Specific host
   
   If you intend to chain Junkbuster and squid locally, then chain as
   browser -> squid -> junkbuster is the recommended way.
   
   Your squid configuration could then look like this:
   
     # Define junkbuster as parent cache
   
     cache_peer 127.0.0.1 parent 8000 0 no-query
   
     # Define ACL for protocol FTP
     acl FTP proto FTP
     # Do not forward ACL FTP to junkbuster
     always_direct allow FTP
     # Do not forward ACL CONNECT (https) to junkbuster
     always_direct allow CONNECT
     # Forward the rest to junkbuster
     never_direct allow all
     _________________________________________________________________
   
3.1.5. Windows GUI Options

   Junkbuster has a number of options specific to the Windows GUI
   interface:
   
   If "activity-animation" is set to 1, the Junkbuster icon will animate
   when "Junkbuster" is active. To turn off, set to 0.
   
     activity-animation 1
   
   If "log-messages" is set to 1, Junkbuster 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, Junkbuster 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 Junkbuster 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 Junkbuster 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
   JunkBuster. If this option is used, Junkbuster will disconnect from
   and hide the command console.
   
     #hide-console
     _________________________________________________________________
   
3.2. The Actions File

   The "actionsfile" is used to define what actions Junkbuster takes, and
   thus determines how images, cookies and various other aspects of HTTP
   content and transactions are handled. Images can be anything you want,
   including ads, banners, or just some obnoxious image that you would
   rather not see. Cookies can be accepted or rejected. The default file
   is in fact named actionsfile.
   
   To determine which actions apply to a request, the URL of the request
   is compared to all patterns in this file. Every time it matches, the
   list of applicable actions for the URL is incrementally updated. You
   can trace this process by visiting [35]http://i.j.b/show-url-info.
   
   The actions file can be edited with a browser by loading
   [36]http://i.j.b, and then select "Edit Actions".
   
   There are four types of lines in this file: comments (begin with a "#"
   character), actions, aliases and patterns, all of which are explained
   below, as well as the configuration file syntax that Junkbuster
   understands.
     _________________________________________________________________
   
3.2.1. URL Domain and Path Syntax

   Generally, a pattern has the form <domain>/<path>, where both the
   <domain> and <path> part are optional. If you only specify a domain
   part, the "/" can be left out:
   
   www.example.com - is a domain only pattern and will match any request
   to "www.example.com".
   
   www.example.com/ - means exactly the same.
   
   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.
   
   index.html - matches nothing, since it would be interpreted as a
   domain name and there is no top-level domain called ".html".
   
   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".
   
   Additionally, there are wildcards that you can use in the domain names
   themselves. They work pretty similar to shell wildcards: "*" stands
   for zero or more arbitrary characters, "?" stands for any single
   character. And you can define charachter classes in square brackets
   and they 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.com - matches "www1.example.com",
   "www4.example.com", "wwwd.example.com", "wwwz.example.com", etc., but
   not "wwww.example.com".
   
   If Junkbuster was compiled with "pcre" support (default), Perl
   compatible regular expressions can be used. See the pcre/docs/
   direcory or "man perlre" (also available on
   [37]http://www.perldoc.com/perl5.6/pod/perlre.html) for details. A
   brief discussion of regular expressions is in the [38]Appendix. For
   instance:
   
   /.*/advert[0-9]+\.jpe?g - would match a URL from any domain, with any
   path that includes "advert" followed immediately by one or more
   digits, then a "." and ending in either "jpeg" or "jpg". So we match
   "example.com/ads/advert2.jpg", and
   "www.example.com/ads/banners/advert39.jpeg", but not
   "www.example.com/ads/banners/advert39.gif" (no gifs in the example
   pattern).
   
   Please 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.
     _________________________________________________________________
   
3.2.2. Actions

   Actions are enabled if preceded with a "+", and disabled if preceded
   with a "-". Actions are invoked by enclosing the action name in curly
   braces (e.g. {+some_action}), followed by a list of URLs to which the
   action applies. There are three classes of actions:
   
     * Boolean (e.g. "+/-block"):
         {+name}        # enable this action
         {-name}        # disable this action
       
     * Parameterized (e.g. "+/-hide-user-agent"):
         {+name{param}}  # enable action and set parameter to "param"
         {-name}         # disable action
       
     * Multi-value (e.g. "{+/-add-header{Name: value}}",
       "{+/-wafer{name=value}}"):
         {+name{param}}   # enable action and add parameter "param"
         {-name{param}}   # remove the parameter "param"
         {-name}          # disable this action totally
       
   If nothing is specified in this file, no "actions" are taken. So in
   this case JunkBuster 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 actionsfile
   file will give a good starting point).
   
   Later defined actions always over-ride earlier ones. For multi-valued
   actions, the actions are applied in the order they are specified.
   
   The list of valid Junkbuster "actions" are:
   
     * Add the specified HTTP header, which is not checked for validity.
       You may specify this many times to specify many different headers:
         +add-header{Name: value}
       
     * Block this URL totally.
         +block
       
     * De-animate all animated GIF images, i.e. reduce them to their last
       frame. 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 propably 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).
         +deanimate-gifs{last}
         +deanimate-gifs{first}
       
     * "+downgrade" will downgrade HTTP/1.1 client requests to HTTP/1.0
       and downgrade the responses as well. Use this action for servers
       that use HTTP/1.1 protocol features that Junkbuster doesn't handle
       well yet. HTTP/1.1 is only partially implemented. Default is not
       to downgrade requests.
         +downgrade
       
     * Many sites, like yahoo.com, don't just link to other sites.
       Instead, they will link to some script on their own server, 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/some_script?http://some.where-else.
       Sometimes, there are even multiple consecutive redirects encoded
       in the URL. These redirections via scripts make your web browing
       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.
       The "+fast-redirects" option enables interception of these
       requests by Junkbuster, who will cut off all but the last valid
       URL in the request and send a local redirect back to your browser
       without contacting the remote site.
         +fast-redirects
       
     * Filter the website through the re_filterfile:
        +filter{filename}
       
     * Block any existing X-Forwarded-for header, and do not add a new
       one:
         +hide-forwarded
       
     * If the browser sends a "From:" header containing your e-mail
       address, this either completely removes the header ("block"), or
       changes it to the specified e-mail address.
         +hide-from{block}
         +hide-from{spam@sittingduck.xqq}
       
     * Don't send the "Referer:" (sic) header to the web site. You can
       block it, forge a URL to the same server as the request (which is
       preferred because some sites will not send images otherwise) or
       set it to a constant string of your choice.
         +hide-referer{block}
         +hide-referer{forge}
         +hide-referer{http://nowhere.com}
       
     * Alternative spelling of "+hide-referer". It has the same
       parameters, and can be freely mixed with, "+hide-referer".
       ("referrer" is the correct English spelling, however the HTTP
       specification has a bug - it requires it to be spelled "referer".)
         +hide-referrer{...}
       
     * Change the "User-Agent:" header so web servers can't tell your
       browser type. Warning! This breaks many web sites. Specify the
       user-agent value you want. Example, pretend to be using Netscape
       on Linux:
         +hide-user-agent{Mozilla (X11; I; Linux 2.0.32 i586)}
       
     * Treat this URL as an image. This only matters if it's also
       "+block"ed, in which case a "blocked" image can be sent rather
       than a HTML page. See "+image-blocker{}" below for the control
       over what is actually sent.
         +image
       
     * Decides what to do with URLs that end up tagged with "{+block
       +image}". There are 4 options. "-image-blocker" will send a HTML
       "blocked" page, usually resulting in a "broken image" icon.
       "+image-blocker{logo}" will send a "JunkBuster" image.
       "+image-blocker{blank}" will send a 1x1 transparent GIF image. And
       finally, "+image-blocker{http://xyz.com}" will send a HTTP
       temporary redirect to the specified image. This has the advantage
       of the icon being being cached by the browser, which will speed up
       the display.
         +image-blocker{logo}
         +image-blocker{blank}
         +image-blocker{http://i.j.b/send-banner}
       
     * By default (i.e. in the absence of a "+limit-connect" action),
       Junkbuster will only allow CONNECT requests to port 443, which is
       the standard port for https as a precaution.
       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
       proxy. This can be a big security hole, since CONNECT-enabled
       proxies can be abused as TCP relays very easily.
       If you want to allow CONNECT for more ports than this, or want to
       forbid CONNECT altogether, you can specify a comma separated list
       of ports and port ranges (the latter using dashes, with the
       minimum defaulting to 0 and max to 65K):
         +limit-connect{443} # This is the default and need no be
       specified.
         +limit-connect{80,443} # Ports 80 and 443 are OK.
         +limit-connect{-3, 7, 20-100, 500-} # Port less than 3, 7, 20 to
       100
          #and above 500 are OK.
       
     * "+no-compression" prevents the website from compressing the data.
       Some websites do this, which can be a problem for Junkbuster,
       since "+filter", "+no-popup" and "+gif-deanimate" will not work on
       compressed data. This will slow down connections to those
       websites, though. Default is "nocompression" is turned on.
         +nocompression
       
     * Prevent the website from reading cookies:
         +no-cookies-read
       
     * Prevent the website from setting cookies:
         +no-cookies-set
       
     * Filter the website through a built-in filter to disable those
       obnoxious JavaScript pop-up windows via window.open(), etc. The
       two alternative spellings are equivalent.
         +no-popup
         +no-popups
       
     * This action only applies if you are using a jarfile for saving
       cookies. It sends a cookie to every site stating that you do not
       accept any copyright on cookies sent to you, and asking them not
       to track you. Of course, this is a (relatively) unique header they
       could use to track you.
         +vanilla-wafer
       
     * This allows you to add an arbitrary cookie. It can be specified
       multiple times in order to add as many cookies as you like.
         +wafer{name=value}
       
   The meaning of any of the above is reversed by preceding the action
   with a "-", in place of the "+".
   
   Some examples:
   
   Turn off cookies by default, then allow a few through for specified
   sites:
   
    # Turn off all cookies
    { +no-cookies-read }
    { +no-cookies-set }
    # Execeptions to the above, sites that need cookies
    { -no-cookies-read }
    { -no-cookies-set }
    .javasoft.com
    .sun.com
    .yahoo.com
    .msdn.microsoft.com
    .redhat.com
    # Alternative way of saying the same thing
    {-no-cookies-set -no-cookies-read}
    .sourceforge.net
    .sf.net
   
   Now turn off "fast redirects", and then we allow two exceptions:
   
    # Turn them off!
    {+fast-redirects}
   
    # Reverse it for these two sites, which don't work right without it.
    {-fast-redirects}
    www.ukc.ac.uk/cgi-bin/wac\.cgi\?
    login.yahoo.com
   
   Turn on page filtering, with one exception for sourceforge:
   
    # Run everything through the default filter file (re_filterfile):
    {+filter}
   
    # But please don't re_filter code from sourceforge!
    {-filter}
    .cvs.sourceforge.net
   
   Now some URLs that we want "blocked", ie we won't see them. Many of
   these use regular expressions that will expand to match multiple URLs:
   
     # Blocklist:
     {+block}
     /.*/(.*[-_.])?ads?[0-9]?(/|[-_.].*|\.(gif|jpe?g))
     /.*/(.*[-_.])?count(er)?(\.cgi|\.dll|\.exe|[?/])
     /.*/(ng)?adclient\.cgi
     /.*/(plain|live|rotate)[-_.]?ads?/
     /.*/(sponsor)s?[0-9]?/
     /.*/_?(plain|live)?ads?(-banners)?/
     /.*/abanners/
     /.*/ad(sdna_image|gifs?)/
     /.*/ad(server|stream|juggler)\.(cgi|pl|dll|exe)
     /.*/adbanners/
     /.*/adserver
     /.*/adstream\.cgi
     /.*/adv((er)?ts?|ertis(ing|ements?))?/
     /.*/banner_?ads/
     /.*/banners?/
     /.*/banners?\.cgi/
     /.*/cgi-bin/centralad/getimage
     /.*/images/addver\.gif
     /.*/images/marketing/.*\.(gif|jpe?g)
     /.*/popupads/
     /.*/siteads/
     /.*/sponsor.*\.gif
     /.*/sponsors?[0-9]?/
     /.*/advert[0-9]+\.jpg
     /Media/Images/Adds/
     /ad_images/
     /adimages/
     /.*/ads/
     /bannerfarm/
     /grafikk/annonse/
     /graphics/defaultAd/
     /image\.ng/AdType
     /image\.ng/transactionID
     /images/.*/.*_anim\.gif # alvin brattli
     /ip_img/.*\.(gif|jpe?g)
     /rotateads/
     /rotations/
     /worldnet/ad\.cgi
     /cgi-bin/nph-adclick.exe/
     /.*/Image/BannerAdvertising/
     /.*/ad-bin/
     /.*/adlib/server\.cgi
     /autoads/
     _________________________________________________________________
   
3.2.3. Aliases

   Custom "actions", known to Junkbuster as "aliases", can be defined by
   combining other "actions". These can in turn be invoked just like the
   built-in "actions". Currently, an alias can contain any character
   except space, tab, "=", "{" or "}". But please use only "a"- "z",
   "0"-"9", "+", and "-". Alias names are not case sensitive, and must be
   defined before anything else in actionsfile! And there can only be one
   set of "aliases" defined.
   
   Now let's define a few aliases:
   
    # Useful customer aliases we can use later. These must come first!
    {{alias}}
    +no-cookies = +no-cookies-set +no-cookies-read
    -no-cookies = -no-cookies-set -no-cookies-read
    fragile     = -block -no-cookies -filter -fast-redirects -hide-refere
   r -no-popups
    shop        = -no-cookies -filter -fast-redirects
    +imageblock = +block +image
    #For people who don't like to type too much:  ;-)
    c0 = +no-cookies
    c1 = -no-cookies
    c2 = -no-cookies-set +no-cookies-read
    c3 = +no-cookies-set -no-cookies-read
    #... etc.  Customize to your heart's content.
   
   Some examples using our "shop" and "fragile" aliases from above:
   
    # These sites are very complex and require
    # minimal interference.
    {fragile}
    .office.microsoft.com
    .windowsupdate.microsoft.com
    .nytimes.com
    # Shopping sites - still want to block ads.
    {shop}
    .quietpc.com
    .worldpay.com   # for quietpc.com
    .jungle.com
    .scan.co.uk
    # These shops require pop-ups
    {shop -no-popups}
    .dabs.com
    .overclockers.co.uk
     _________________________________________________________________
   
3.3. The Filter File

   The filter file defines what filtering of web pages Junkbuster does.
   The default filter file is re_filterfile, located in the config
   directory. In this file, any document content, whether viewable text
   or embedded non-visible content, can be changed.
   
   This file uses regular expressions to alter or remove any string in
   the target page. Some examples from the included default
   re_filterfile:
   
   Stop web pages from displaying annoying messages in the status bar by
   deleting such references:
   
    # The status bar is for displaying link targets, not pointless buzzwo
   rds.
    # Again, check it out on http://www.airport-cgn.de/.
    s/status='.*?';*//ig
   
   Just for kicks, replace any occurrence of "Microsoft" with
   "MicroSuck":
   
    s/microsoft(?!.com)/MicroSuck/ig
   
   Kill those auto-refresh tags:
   
    # Kill refresh tags. I like to refresh myself. Manually.
    # check it out on http://www.airport-cgn.de/ and go to the arrivals p
   age.
    #
    s/<meta[^>]*http-equiv[^>]*refresh.*URL=([^>]*?)"?>/<link rev="x-refr
   esh" href=$1>/i
    s/<meta[^>]*http-equiv="?page-enter"?[^>]*content=[^>]*>/<!--no page
   enter for me-->/i
     _________________________________________________________________
   
4. Quickstart to Using Junkbuster

   Install package, then run and enjoy! Junbuster accepts only one
   command line option -- the configuration file to be used. Example Unix
   startup command:
   

 # /usr/sbin/junkbuster /etc/junkbuster/config &


   If no configuration file is specified on the command line, Junkbuster
   will look for a file named config in the current directory. Except on
   Amiga where it will look for AmiTCP:db/junkbuster/config and Win32
   where it will try junkbstr.txt. If no file is specified on the command
   line and no default configuration file can be found, Junkbuster will
   fail to start.
   
   Be sure your browser is set to use the proxy which is by default at
   localhost, port 8000. 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: localhost, Port: 8000). Include if HTTPS proxy support too.
   
   The included default configuration files should give a reasonable
   starting point, though may be somewhat aggressive in blocking junk.
   You will probably want to keep an eye out for sites that require
   cookies, and add these to actionsfile as needed. By default, most of
   these will be blocked until you add them to the configuration. If you
   want the browser to handle this instead, you will need to edit
   actionsfile and disable this feature. If you use more than one
   browser, it would make more sense to let Junkbuster handle this. In
   which case, the browser(s) should be set to accept all cookies.
   
   If a particular site shows problems loading properly, try adding it to
   the {fragile} section of actionsfile. This will turn off most actions
   for this site.
   
   HTTP/1.1 support is not fully implemented. If browsers that support
   HTTP/1.1 (like Mozilla or recent versions of I.E.) experience
   problems, you might try to force HTTP/1.0 compatiblity. For Mozilla,
   look under Edit -> Preferences -> Debug -> Networking. Or set the
   "+downgrade" config option in actionsfile.
   
   After running Junkbuster for a while, you can start to fine tune the
   configuration to suit your personal, or site, preferences and
   requirements. There are many, many aspects that can be customized.
   "Actions" (from actionsfile) can be adjusted by pointing your browser
   to [39]http://i.j.b./, and then follow the link to "edit the actions
   list". (This is an internal page and does not require Internet
   access.)
   
   In fact, various aspects of Junkbuster configuration can be viewed
   from this page, including current configuration parameters, source
   code version numbers, the browser's request headers, and "actions"
   that apply to a given URL. In addition to the actionsfile editor
   mentioned above, Junkbuster can also be turned "on" and "off" from
   this page.
   
   If you encounter problems, please verify it is a Junkbuster bug, by
   disabling Junkbuster, and then trying the same page. Also, try another
   browser if possible to eliminate browser or site problems. Before
   reporting it as a bug, see if there is not a configuration option that
   is enabled that is causing the page not to load. You can then add an
   exception for that page or site. If a bug, please report it to the
   developers (see below).
     _________________________________________________________________
   
5. Contact the Developers

   Feature requests and other questions should be posted to the
   [40]Feature request page at SourceForge. There is also an archive
   there.
   
   Anyone interested in actively participating in development and related
   discussions can join the appropriate mailing list [41]here. Archives
   are available here too.
   
   Please report bugs, using the form at [42]Sourceforge. Please try to
   verify that it is a Junkbuster bug, and not a browser or site bug
   first. Also, check to make sure this is not already a known bug.
     _________________________________________________________________
   
6. Copyright and History

6.1. License

   Internet Junkbuster is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.
   
   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
   [43]the Free Software Foundation, Inc, 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.
     _________________________________________________________________
   
6.2. History

   Junkbuster was originally written by Anonymous Coders and
   [44]JunkBusters Corporation, and was released as free open-source
   software under the GNU GPL. [45]Stefan Waldherr made many
   improvements, and started the [46]SourceForge project to rekindle
   development. The last stable release was v2.0.2, which has now grown
   whiskers ;-).
     _________________________________________________________________
   
7. See also

     [47]http://sourceforge.net/projects/ijbswa
   
     [48]http://ijbswa.sourceforge.net/
   
     [49]http://i.j.b./
   
     [50]http://www.junkbusters.com/ht/en/cookies.html
   
     [51]http://www.waldherr.org/junkbuster/
   
     [52]http://privacy.net/analyze/
   
    [53]http://www.squid-cache.org/
     _________________________________________________________________
   
8. Appendix

8.1. Regular Expressions

   Junkbuster 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 wildcards 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
   wildcards, and other special characters, called metacharacters. The
   "metacharacters" 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 wildcard
   characters when listing files with the dir command in DOS. *.* matches
   all filenames. The "special" character here is the asterik 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
   metacharacter.
   
   [] - Characters enclosed in brackets will be matched if any of the
   enclosed characters are encountered.
   
   () - Pararentheses 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.
   
   s/string1/string2/g - This is used to rewrite strings of text.
   "string1" is replaced by "string2" in this example.
   
   These are just some of the ones you are likely to use when matching
   URLs with Junkbuster, 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 occurence 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 Junkbuster 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:
   [54]http://www.perldoc.com/perl5.6/pod/perlre.html

References

   1. http://ijbswa.sourceforge.net/user-manual/
   2. mailto:ijbswa-developers@lists.sourceforge.net
   3. file://localhost/home/swa/sf/current/doc/source/tmp.html#INTRODUCTION
   4. file://localhost/home/swa/sf/current/doc/source/tmp.html#AEN27
   5. file://localhost/home/swa/sf/current/doc/source/tmp.html#INSTALLATION
   6. file://localhost/home/swa/sf/current/doc/source/tmp.html#INSTALLATION-SOURCE
   7. file://localhost/home/swa/sf/current/doc/source/tmp.html#INSTALLATION-RH
   8. file://localhost/home/swa/sf/current/doc/source/tmp.html#INSTALLATION-SUSE
   9. file://localhost/home/swa/sf/current/doc/source/tmp.html#INSTALLATION-OS2
  10. file://localhost/home/swa/sf/current/doc/source/tmp.html#INSTALLATION-WIN
  11. file://localhost/home/swa/sf/current/doc/source/tmp.html#INSTALLATION-OTHER
  12. file://localhost/home/swa/sf/current/doc/source/tmp.html#CONFIGURATION
  13. file://localhost/home/swa/sf/current/doc/source/tmp.html#AEN158
  14. file://localhost/home/swa/sf/current/doc/source/tmp.html#ACTIONSFILE
  15. file://localhost/home/swa/sf/current/doc/source/tmp.html#FILTERFILE
  16. file://localhost/home/swa/sf/current/doc/source/tmp.html#QUICKSTART
  17. file://localhost/home/swa/sf/current/doc/source/tmp.html#CONTACT
  18. file://localhost/home/swa/sf/current/doc/source/tmp.html#COPYRIGHT
  19. file://localhost/home/swa/sf/current/doc/source/tmp.html#AEN1161
  20. file://localhost/home/swa/sf/current/doc/source/tmp.html#AEN1167
  21. file://localhost/home/swa/sf/current/doc/source/tmp.html#SEEALSO
  22. file://localhost/home/swa/sf/current/doc/source/tmp.html#APPENDIX
  23. file://localhost/home/swa/sf/current/doc/source/tmp.html#REGEX
  24. http://i.j.b/
  25. http://sourceforge.net/projects/ijbswa/
  26. http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/ijbswa/current/
  27. http://hobbes.nmsu.edu/cgi-bin/h-search?sh=1&button=Search&key=emxrt.zip&stype=all&sort=type&dir=%2Fpub%2Fos2%2Fdev%2Femx%2Fv0.9d
  28. http://hobbes.nmsu.edu/cgi-bin/h-search?sh=1&key=gnupack&stype=all&sort=type&dir=%2Fpub%2Fos2%2Fapps
  29. http://www.gnu.org/
  30. http://i.j.b/
  31. file://localhost/home/swa/sf/current/doc/source/tmp.html#ACTIONSFILE
  32. http://i.j.b/
  33. http://i.j.b/
  34. http://i.j.b/
  35. http://i.j.b/show-url-info
  36. http://i.j.b/
  37. http://www.perldoc.com/perl5.6/pod/perlre.html
  38. file://localhost/home/swa/sf/current/doc/source/tmp.html#REGEX
  39. http://i.j.b/
  40. http://sourceforge.net/tracker/?atid=361118&group_id=11118&func=browse
  41. http://sourceforge.net/mail/?group_id=11118
  42. http://sourceforge.net/tracker/?group_id=11118&atid=111118
  43. http://www.gnu.org/copyleft/gpl.html
  44. http://www.junkbusters.com/ht/en/ijbfaq.html
  45. http://www.waldherr.org/junkbuster/
  46. http://sourceforge.net/projects/ijbswa/
  47. http://sourceforge.net/projects/ijbswa
  48. http://ijbswa.sourceforge.net/
  49. http://i.j.b/
  50. http://www.junkbusters.com/ht/en/cookies.html
  51. http://www.waldherr.org/junkbuster/
  52. http://privacy.net/analyze/
  53. http://www.squid-cache.org/
  54. http://www.perldoc.com/perl5.6/pod/perlre.html