Fix typo.

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

Junkbuster User Manual

By: Junkbuster Developers

$Id: user-manual.sgml,v 1.23 2001/12/02 00:20:41 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 http://
ijbswa.sourceforge.net/user-manual/.

Feel free to send a note to the developers at <
ijbswa-developers@lists.sourceforge.net>.

-------------------------------------------------------------------------------

Table of Contents
1. Introduction
   
    1.1. New Features
   
2. Installation
   
    2.1. Source
    2.2. Red Hat
    2.3. SuSE
    2.4. OS/2
    2.5. Windows
    2.6. Other
   
3. Junkbuster Configuration
   
    3.1. The Main Configuration File
    3.2. The Actions File
    3.3. The Filter File
   
4. Quickstart to Using Junkbuster
5. Contact the Developers
6. Copyright and History
   
    6.1. License
    6.2. History
   
7. See also
8. Appendix
   
    8.1. 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 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 
Junkbuster Home Page for current release info. Junkbuster is also available via
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 xzvf ijb_source_* [.tgz or .tar.gz]                                       
 cd ijb_source_2.9.9_alpha                                                     
                                                                               

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 current 
  cd current                                                                         
                                                                                     

This will create a directory named current/, which will contain the source
tree.

Then, in either case, to build from tarball/CVS source:

 ./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)                                        
                                                                               

For Redhat and SuSE Linux RPM packages, see below.

-------------------------------------------------------------------------------

2.2. Red Hat

To build Redhat RPM packages, install source as above. Then:

 autoheader   [suggested for CVS source]                                       
 autoconf     [suggested 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:

 autoheader   [suggested for CVS source]                                       
 autoconf     [suggested for CVS source]                                       
 ./configure                                                                   
 make suse-dist                                                                
                                                                               

This will create both binary and src RPMs in the usual places. Example:

   /usr/src/packages/RPMS/i686/junkbuster-2.9.9-1.i686.rpm

   /usr/src/packages/SRPMS/junkbuster-2.9.9-1.src.rpm

To install, of course:

 rpm -Uvv /usr/src/packages/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: 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

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: 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 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 config.txt on Windows. On Amiga, it is AmiTCP:db/junkbuster/config.
   
  * The ijb.action 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 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.
   
ijb.action 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 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:

  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 "ijb.action" file contains patterns to specify the actions to apply to
requests for each site. Default: Cookies to and from all destinations are kept
only during the current browser session (i.e. they are not saved to disk).
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 below.

  actionsfile ijb.action
   

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 would
otherwise have blocked. This can also be toggled via a web browser at the
Junkbuster internal address of 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 ijb.action file 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 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 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 requests 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 should
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 "ijb.action" file (formerly 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, or accepted only during
the current browser session (i.e. not written to disk).

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 http://i.j.b/show-url-info.

The actions file can be edited with a browser by loading 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 http://www.perldoc.com/perl5.6/pod/perlre.html) for details.
A brief discussion of regular expressions is in the 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 ijb.action 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
         
   
  * If the website sets cookies, "no-cookies-keep" will make sure they are
    erased when you exit and restart your web browser. This makes profiling
    cookies useless, but won't break sites which require cookies so that you
    can log in for transactions. Default: on.
   
      +no-cookies-keep
         
   
  * 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 persistant cookies
 { +no-cookies-read }
 { +no-cookies-set }
 # Allow cookies for this browser session ONLY
 { +no-cookies-keep }

 # Execeptions to the above, sites that benefit from persistant cookies
 { -no-cookies-read }
 { -no-cookies-set }
 { -no-cookies-keep }
 .javasoft.com
 .sun.com
 .yahoo.com
 .msdn.microsoft.com
 .redhat.com

 # Alternative way of saying the same thing
 {-no-cookies-set -no-cookies-read -no-cookies-keep}
 .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 the ijb.actionfile
! 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-referer -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 buzzwords.
 # 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 page.
 #
 s/<meta[^>]*http-equiv[^>]*refresh.*URL=([^>]*?)"?>/<link rev="x-refresh" 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                                 
                                                                               
                                                                               

An init script is provided for SuSE and Redhat.

For for SuSE: /etc/rc.d/junkbuster start

For RedHat: /etc/rc.d/init.d/junkbuster start

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 config.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 persistant cookies, and add
these to ijb.action as needed. By default, most of these will be accepted only
during the current browser session, until you add them to the configuration. If
you want the browser to handle this instead, you will need to edit ijb.action
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 ijb.action. 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 ijb.action.

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" (as specified in
ijb.action) can be adjusted by pointing your browser to 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 ijb.action file 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 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 here. Archives are available
here too.

Please report bugs, using the form at 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 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 JunkBusters
Corporation, and was released as free open-source software under the GNU GPL. 
Stefan Waldherr made many improvements, and started the SourceForge project to
rekindle development. The last stable release was v2.0.2, which has now grown
whiskers ;-).

-------------------------------------------------------------------------------

7. See also

  http://sourceforge.net/projects/ijbswa

  http://ijbswa.sourceforge.net/

  http://i.j.b/

  http://www.junkbusters.com/ht/en/cookies.html

  http://www.waldherr.org/junkbuster/

  http://privacy.net/analyze/

 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: http://www.perldoc.com/
perl5.6/pod/perlre.html