+-------------------------------------------------------------------------------
+
+8. Actions Files
+
+The actions files are used to define what actions Privoxy takes for which URLs,
+and thus determine how ad images, cookies and various other aspects of HTTP
+content and transactions are handled, and on which sites (or even parts
+thereof). There are three such files included with Privoxy with differing
+purposes:
+
+ * default.action - is the primary action file that sets the initial values
+ for all actions. It is intended to provide a base level of functionality
+ for Privoxy's array of features. So it is a set of broad rules that should
+ work reasonably well for users everywhere. This is the file that the
+ developers are keeping updated, and making available to users.
+
+ * user.action - is intended to be for local site preferences and exceptions.
+ As an example, if your ISP or your bank has specific requirements, and need
+ special handling, this kind of thing should go here. This file will not be
+ upgraded.
+
+ * standard.action - is used by the web based editor, to set various
+ pre-defined sets of rules for the default actions section in
+ default.action. These have increasing levels of aggressiveness and have no
+ influence on your browsing unless you select them explicitly in the editor.
+ It is not recommend to edit this file.
+
+ The default profiles, and their associated actions, as pre-defined in
+ standard.action are:
+
+ Table 1. Default Configurations
+
+ +------------------------------------------------------------+
+ | Feature | Cautious | Medium |Adventuresome|
+ |---------------------+-----------+------------+-------------|
+ |Ad-blocking by URL |yes |yes |yes |
+ |---------------------+-----------+------------+-------------|
+ |Ad-filtering by size |yes |yes |yes |
+ |---------------------+-----------+------------+-------------|
+ |GIF de-animation |no |yes |yes |
+ |---------------------+-----------+------------+-------------|
+ |Referer forging |no |yes |yes |
+ |---------------------+-----------+------------+-------------|
+ |Cookie handling |none |session-only|kill |
+ |---------------------+-----------+------------+-------------|
+ |Pop-up killing |unsolicited|unsolicited |all |
+ |---------------------+-----------+------------+-------------|
+ |Fast redirects |no |no |yes |
+ |---------------------+-----------+------------+-------------|
+ |HTML taming |yes |yes |yes |
+ |---------------------+-----------+------------+-------------|
+ |JavaScript taming |yes |yes |yes |
+ |---------------------+-----------+------------+-------------|
+ |Web-bug killing |yes |yes |yes |
+ |---------------------+-----------+------------+-------------|
+ |Fun text replacements|no |no |yes |
+ |---------------------+-----------+------------+-------------|
+ |Image tag reordering |no |no |yes |
+ |---------------------+-----------+------------+-------------|
+ |Ad-filtering by link |no |no |yes |
+ |---------------------+-----------+------------+-------------|
+ |Demoronizer |no |no |yes |
+ +------------------------------------------------------------+
+
+The list of actions files to be used are defined in the main configuration
+file, and are processed in the order they are defined (e.g. default.action is
+typically process before user.action). The content of these can all be viewed
+and edited from http://config.privoxy.org/show-status.
+
+An actions file typically has multiple sections. If you want to use "aliases"
+in an actions file, you have to place the (optional) alias section at the top
+of that file. Then comes the default set of rules which will apply universally
+to all sites and pages (be very careful with using such a universal set in
+user.action or any other actions file after default.action, because it will
+override the result from consulting any previous file). And then below that,
+exceptions to the defined universal policies. You can regard user.action as an
+appendix to default.action, with the advantage that is a separate file, which
+makes preserving your personal settings across Privoxy upgrades easier.
+
+Actions can be used to block anything you want, including ads, banners, or just
+some obnoxious URL that you would rather not see. Cookies can be accepted or
+rejected, or accepted only during the current browser session (i.e. not written
+to disk), content can be modified, JavaScripts tamed, user-tracking fooled, and
+much more. See below for a complete list of actions.
+
+-------------------------------------------------------------------------------
+
+8.1. Finding the Right Mix
+
+Note that some actions, like cookie suppression or script disabling, may render
+some sites unusable that rely on these techniques to work properly. Finding the
+right mix of actions is not always easy and certainly a matter of personal
+taste. In general, it can be said that the more "aggressive" your default
+settings (in the top section of the actions file) are, the more exceptions for
+"trusted" sites you will have to make later. If, for example, you want to
+crunch all cookies per default, you'll have to make exceptions from that rule
+for sites that you regularly use and that require cookies for actually useful
+puposes, like maybe your bank, favorite shop, or newspaper.
+
+We have tried to provide you with reasonable rules to start from in the
+distribution actions files. But there is no general rule of thumb on these
+things. There just are too many variables, and sites are constantly changing.
+Sooner or later you will want to change the rules (and read this chapter again
+:).
+
+-------------------------------------------------------------------------------
+
+8.2. How to Edit
+
+The easiest way to edit the actions files is with a browser by using our
+browser-based editor, which can be reached from http://config.privoxy.org/
+show-status. The editor allows both fine-grained control over every single
+feature on a per-URL basis, and easy choosing from wholesale sets of defaults
+like "Cautious", "Medium" or "Adventuresome". Warning: the "Adventuresome"
+setting is not only more aggressive, but includes settings that are fun and
+subversive, and which some may find of dubious merit!
+
+If you prefer plain text editing to GUIs, you can of course also directly edit
+the the actions files. Look at default.action which is richly commented.
+
+-------------------------------------------------------------------------------
+
+8.3. How Actions are Applied to URLs
+
+Actions files are divided into sections. There are special sections, like the "
+alias" sections which will be discussed later. For now let's concentrate on
+regular sections: They have a heading line (often split up to multiple lines
+for readability) which consist of a list of actions, separated by whitespace
+and enclosed in curly braces. Below that, there is a list of URL patterns, each
+on a separate line.
+
+To determine which actions apply to a request, the URL of the request is
+compared to all patterns in each action file file. Every time it matches, the
+list of applicable actions for the URL is incrementally updated, using the
+heading of the section in which the pattern is located. If multiple matches for
+the same URL set the same action differently, the last match wins. If not, the
+effects are aggregated. E.g. a URL might match a regular section with a heading
+line of { +handle-as-image }, then later another one with just { +block },
+resulting in both actions to apply.
+
+You can trace this process for any given URL by visiting http://
+config.privoxy.org/show-url-info.
+
+More detail on this is provided in the Appendix, Anatomy of an Action.
+
+-------------------------------------------------------------------------------
+
+8.4. Patterns
+
+As mentioned, Privoxy uses "patterns" to determine what actions might apply to
+which sites and pages your browser attempts to access. These "patterns" use
+wild card type pattern matching to achieve a high degree of flexibility. This
+allows one expression to be expanded and potentially match against many similar
+patterns.
+
+Generally, a Privoxy pattern has the form <domain>/<path>, where both the
+<domain> and <path> are optional. (This is why the special / pattern matches
+all URLs). Note that the protocol portion of the URL pattern (e.g. http://)
+should not be included in the pattern. This is assumed already!
+
+www.example.com/
+
+ is a domain-only pattern and will match any request to www.example.com,
+ regardless of which document on that server is requested.
+
+www.example.com
+
+ means exactly the same. For domain-only patterns, the trailing / may be
+ omitted.
+
+www.example.com/index.html
+
+ matches only the single document /index.html on www.example.com.
+
+/index.html
+
+ matches the document /index.html, regardless of the domain, i.e. on any web
+ server.
+
+index.html
+
+ matches nothing, since it would be interpreted as a domain name and there
+ is no top-level domain called .html.
+
+-------------------------------------------------------------------------------
+
+8.4.1. The Domain Pattern
+
+The matching of the domain part offers some flexible options: if the domain
+starts or ends with a dot, it becomes unanchored at that end. For example:
+
+.example.com
+
+ matches any domain that ENDS in .example.com
+
+www.
+
+ matches any domain that STARTS with www.
+
+.example.
+
+ matches any domain that CONTAINS .example. (Correctly speaking: It matches
+ any FQDN that contains example as a domain.)
+
+Additionally, there are wild-cards that you can use in the domain names
+themselves. They work pretty similar to shell wild-cards: "*" stands for zero
+or more arbitrary characters, "?" stands for any single character, you can
+define character classes in square brackets and all of that can be freely
+mixed:
+
+ad*.example.com
+
+ matches "adserver.example.com", "ads.example.com", etc but not
+ "sfads.example.com"
+
+*ad*.example.com
+
+ matches all of the above, and then some.
+
+.?pix.com
+
+ matches www.ipix.com, pictures.epix.com, a.b.c.d.e.upix.com etc.
+
+www[1-9a-ez].example.c*
+
+ matches www1.example.com, www4.example.cc, wwwd.example.cy,
+ wwwz.example.com etc., but not wwww.example.com.
+
+-------------------------------------------------------------------------------
+
+8.4.2. The Path Pattern
+
+Privoxy uses Perl compatible regular expressions (through the PCRE library) for
+matching the path.
+
+There is an Appendix with a brief quick-start into regular expressions, and
+full (very technical) documentation on PCRE regex syntax is available on-line
+at http://www.pcre.org/man.txt. You might also find the Perl man page on
+regular expressions (man perlre) useful, which is available on-line at http://
+www.perldoc.com/perl5.6/pod/perlre.html.
+
+Note that the path pattern is automatically left-anchored at the "/", i.e. it
+matches as if it would start with a "^" (regular expression speak for the
+beginning of a line).
+
+Please also note that matching in the path is CASE INSENSITIVE by default, but
+you can switch to case sensitive at any point in the pattern by using the "(?
+-i)" switch: www.example.com/(?-i)PaTtErN.* will match only documents whose
+path starts with PaTtErN in exactly this capitalization.
+
+-------------------------------------------------------------------------------
+
+8.5. Actions
+
+All actions are disabled by default, until they are explicitly enabled
+somewhere in an actions file. Actions are turned on if preceded with a "+", and
+turned off if preceded with a "-". So a +action means "do that action", e.g.
++block means "please block URLs that match the following patterns", and -block
+means "don't block URLs that match the following patterns, even if +block
+previously applied."
+
+Again, actions are invoked by placing them on a line, enclosed in curly braces
+and separated by whitespace, like in {+some-action -some-other-action
+{some-parameter}}, followed by a list of URL patterns, one per line, to which
+they apply. Together, the actions line and the following pattern lines make up
+a section of the actions file.
+
+There are three classes of actions:
+
+ * Boolean, i.e the action can only be "enabled" or "disabled". Syntax:
+
+ +name # enable action name
+ -name # disable action name
+
+
+ Example: +block
+
+ * Parameterized, where some value is required in order to enable this type of
+ action. Syntax:
+
+ +name{param} # enable action and set parameter to param,
+ # overwriting parameter from previous match if necessary
+ -name # disable action. The parameter can be omitted
+
+
+ Note that if the URL matches multiple positive forms of a parameterized
+ action, the last match wins, i.e. the params from earlier matches are
+ simply ignored.
+
+ Example: +hide-user-agent{ Mozilla 1.0 }
+
+ * Multi-value. These look exactly like parameterized actions, but they behave
+ differently: If the action applies multiple times to the same URL, but with
+ different parameters, all the parameters from all matches are remembered.
+ This is used for actions that can be executed for the same request
+ repeatedly, like adding multiple headers, or filtering through multiple
+ filters. Syntax:
+
+ +name{param} # enable action and add param to the list of parameters
+ -name{param} # remove the parameter param from the list of parameters
+ # If it was the last one left, disable the action.
+ -name # disable this action completely and remove all parameters from the list
+
+
+ Examples: +add-header{X-Fun-Header: Some text} and +filter{html-annoyances}
+
+If nothing is specified in any actions file, no "actions" are taken. So in this
+case Privoxy would just be a normal, non-blocking, non-anonymizing proxy. You
+must specifically enable the privacy and blocking features you need (although
+the provided default actions files will give a good starting point).
+
+Later defined actions always over-ride earlier ones. So exceptions to any rules
+you make, should come in the latter part of the file (or in a file that is
+processed later when using multiple actions files). For multi-valued actions,
+the actions are applied in the order they are specified. Actions files are
+processed in the order they are defined in config (the default installation has
+three actions files). It also quite possible for any given URL pattern to match
+more than one pattern and thus more than one set of actions!
+
+The list of valid Privoxy actions are:
+
+-------------------------------------------------------------------------------
+
+8.5.1. add-header
+
+Typical use:
+
+ Confuse log analysis, custom applications
+
+Effect:
+
+ Sends a user defined HTTP header to the web server.
+
+Type:
+
+ Multi-value.
+
+Parameter:
+
+ Any string value is possible. Validity of the defined HTTP headers is not
+ checked. It is recommended that you use the "X-" prefix for custom headers.
+
+Notes:
+
+ This action may be specified multiple times, in order to define multiple
+ headers. This is rarely needed for the typical user. If you don't know what
+ "HTTP headers" are, you definitely don't need to worry about this one.
+
+Example usage:
+
+ +add-header{X-User-Tracking: sucks}
+
+
+-------------------------------------------------------------------------------
+
+8.5.2. block
+
+Typical use:
+
+ Block ads or other obnoxious content
+
+Effect:
+
+ Requests for URLs to which this action applies are blocked, i.e. the
+ requests are not forwarded to the remote server, but answered locally with
+ a substitute page or image, as determined by the handle-as-image and
+ set-image-blocker actions.
+
+Type:
+
+ Boolean.
+
+Parameter:
+
+ N/A
+
+Notes:
+
+ Privoxy sends a special "BLOCKED" page for requests to blocked pages. This
+ page contains links to find out why the request was blocked, and a
+ click-through to the blocked content (the latter only if compiled with the
+ force feature enabled). The "BLOCKED" page adapts to the available screen
+ space -- it displays full-blown if space allows, or miniaturized and
+ text-only if loaded into a small frame or window. If you are using Privoxy
+ right now, you can take a look at the "BLOCKED" page.
+
+ A very important exception occurs if both block and handle-as-image, apply
+ to the same request: it will then be replaced by an image. If
+ set-image-blocker (see below) also applies, the type of image will be
+ determined by its parameter, if not, the standard checkerboard pattern is
+ sent.
+
+ It is important to understand this process, in order to understand how
+ Privoxy deals with ads and other unwanted content.
+
+ The filter action can perform a very similar task, by "blocking" banner
+ images and other content through rewriting the relevant URLs in the
+ document's HTML source, so they don't get requested in the first place.
+ Note that this is a totally different technique, and it's easy to confuse
+ the two.
+
+Example usage (section):
+
+ {+block} # Block and replace with "blocked" page
+ .nasty-stuff.example.com
+
+ {+block +handle-as-image} # Block and replace with image
+ .ad.doubleclick.net
+ .ads.r.us
+
+
+-------------------------------------------------------------------------------
+
+8.5.3. crunch-incoming-cookies
+
+Typical use:
+
+ Prevent the web server from setting any cookies on your system
+
+Effect:
+
+ Deletes any "Set-Cookie:" HTTP headers from server replies.
+
+Type:
+
+ Boolean.
+
+Parameter:
+
+ N/A
+
+Notes:
+
+ This action is only concerned with incoming cookies. For outgoing cookies,
+ use crunch-outgoing-cookies. Use both to disable cookies completely.
+
+ It makes no sense at all to use this action in conjunction with the
+ session-cookies-only action, since it would prevent the session cookies
+ from being set. See also filter-content-cookies.
+
+Example usage:
+
+ +crunch-incoming-cookies
+
+
+-------------------------------------------------------------------------------
+
+8.5.4. crunch-outgoing-cookies
+
+Typical use:
+
+ Prevent the web server from reading any cookies from your system
+
+Effect:
+
+ Deletes any "Cookie:" HTTP headers from client requests.
+
+Type:
+
+ Boolean.
+
+Parameter:
+
+ N/A
+
+Notes:
+
+ This action is only concerned with outgoing cookies. For incoming cookies,
+ use crunch-incoming-cookies. Use both to disable cookies completely.
+
+ It makes no sense at all to use this action in conjunction with the
+ session-cookies-only action, since it would prevent the session cookies
+ from being read.
+
+Example usage:
+
+ +crunch-outgoing-cookies
+
+
+-------------------------------------------------------------------------------
+
+8.5.5. deanimate-gifs
+
+Typical use:
+
+ Stop those annoying, distracting animated GIF images.
+
+Effect:
+
+ De-animate GIF animations, i.e. reduce them to their first or last image.
+
+Type:
+
+ Parameterized.
+
+Parameter:
+
+ "last" or "first"
+
+Notes:
+
+ This will also shrink the images considerably (in bytes, not pixels!). If
+ the option "first" is given, the first frame of the animation is used as
+ the replacement. If "last" is given, the last frame of the animation is
+ used instead, which probably makes more sense for most banner animations,
+ but also has the risk of not showing the entire last frame (if it is only a
+ delta to an earlier frame).
+
+ You can safely use this action with patterns that will also match non-GIF
+ objects, because no attempt will be made at anything that doesn't look like
+ a GIF.
+
+Example usage:
+
+ +deanimate-gifs{last}
+
+
+-------------------------------------------------------------------------------
+
+8.5.6. downgrade-http-version
+
+Typical use:
+
+ Work around (very rare) problems with HTTP/1.1
+
+Effect:
+
+ Downgrades HTTP/1.1 client requests and server replies to HTTP/1.0.
+
+Type:
+
+ Boolean.
+
+Parameter:
+
+ N/A
+
+Notes:
+
+ This is a left-over from the time when Privoxy didn't support important
+ HTTP/1.1 features well. It is left here for the unlikely case that you
+ experience HTTP/1.1 related problems with some server out there. Not all
+ (optional) HTTP/1.1 features are supported yet, so there is a chance you
+ might need this action.
+
+Example usage (section):
+
+ {+downgrade-http-version}
+ problem-host.example.com
+
+
+-------------------------------------------------------------------------------
+
+8.5.7. fast-redirects
+
+Typical use:
+
+ Fool some click-tracking scripts and speed up indirect links
+
+Effect:
+
+ Cut off all but the last valid URL from requests.
+
+Type:
+
+ Boolean.
+
+Parameter:
+
+ N/A
+
+Notes:
+
+ Many sites, like yahoo.com, don't just link to other sites. Instead, they
+ will link to some script on their own servers, giving the destination as a
+ parameter, which will then redirect you to the final target. URLs resulting
+ from this scheme typically look like: http://some.place/click-tracker.cgi?
+ target=http://some.where.else.
+
+ Sometimes, there are even multiple consecutive redirects encoded in the
+ URL. These redirections via scripts make your web browsing more traceable,
+ since the server from which you follow such a link can see where you go to.
+ Apart from that, valuable bandwidth and time is wasted, while your browser
+ ask the server for one redirect after the other. Plus, it feeds the
+ advertisers.
+
+ This feature is currently not very smart and is scheduled for improvement.
+ It is likely to break some sites. You should expect to need possibly many
+ exceptions to this action, if it is enabled by default in default.action.
+ Some sites just don't work without it.
+
+Example usage:
+
+ {+fast-redirects}
+
+
+-------------------------------------------------------------------------------
+
+8.5.8. filter
+
+Typical use:
+
+ Get rid of HTML and JavaScript annoyances, banner advertisements (by size),
+ do fun text replacements, etc.
+
+Effect:
+
+ All files of text-based type, most notably HTML and JavaScript, to which
+ this action applies, are filtered on-the-fly through the specified regular
+ expression based substitutions. (Note: as of version 3.0.3 plain text
+ documents are exempted from filtering, because web servers often use the
+ text/plain MIME type for all files whose type they don't know.)
+
+Type:
+
+ Parameterized.
+
+Parameter:
+
+ The name of a filter, as defined in the filter file (typically
+ default.filter, set by the filterfile option in the config file). When used
+ in its negative form, and without parameters, filtering is completely
+ disabled.
+
+Notes:
+
+ For your convenience, there are a number of pre-defined filters available
+ in the distribution filter file that you can use. See the examples below
+ for a list.
+
+ Filtering requires buffering the page content, which may appear to slow
+ down page rendering since nothing is displayed until all content has passed
+ the filters. (It does not really take longer, but seems that way since the
+ page is not incrementally displayed.) This effect will be more noticeable
+ on slower connections.
+
+ This is very powerful feature, but "rolling your own" filters requires a
+ knowledge of regular expressions and HTML.
+
+ The amount of data that can be filtered is limited to the buffer-limit
+ option in the main config file. The default is 4096 KB (4 Megs). Once this
+ limit is exceeded, the buffered data, and all pending data, is passed
+ through unfiltered.
+
+ Inadequate MIME types, such as zipped files, are not filtered at all.
+ (Again, only text-based types except plain text). Encrypted SSL data (from
+ HTTPS servers) cannot be filtered either, since this would violate the
+ integrity of the secure transaction. In some situations it might be
+ necessary to protect certain text, like source code, from filtering by
+ defining appropriate -filter sections.
+
+ At this time, Privoxy cannot (yet!) uncompress compressed documents. If you
+ want filtering to work on all documents, even those that would normally be
+ sent compressed, use the prevent-compression action in conjunction with
+ filter.
+
+ Filtering can achieve some of the same effects as the block action, i.e. it
+ can be used to block ads and banners. But the mechanism works quite
+ differently. One effective use, is to block ad banners based on their size
+ (see below), since many of these seem to be somewhat standardized.
+
+ Feedback with suggestions for new or improved filters is particularly
+ welcome!
+
+ The below list has only the names and a one-line description of each
+ predefined filter. There are more verbose explanations of what these
+ filters do in the filter file chapter.
+
+Example usage (with filters from the distribution default.filter file). See the
+ Predefined Filters section for more explanation on each:
+
+ +filter{js-annoyances} # Get rid of particularly annoying JavaScript abuse
+
+
+ +filter{js-events} # Kill all JS event bindings (Radically destructive! Only for extra nasty sites)
+
+
+ +filter{html-annoyances} # Get rid of particularly annoying HTML abuse
+
+
+ +filter{content-cookies} # Kill cookies that come in the HTML or JS content
+
+
+ +filter{refresh-tags} # Kill automatic refresh tags (for dial-on-demand setups)
+
+
+ +filter{unsolicited-popups} # Disable only unsolicited pop-up windows
+
+
+ +filter{all-popups} # Kill all popups in JavaScript and HTML
+
+
+ +filter{img-reorder} # Reorder attributes in <img> tags to make the banners-by-* filters more effective
+
+
+ +filter{banners-by-size} # Kill banners by size
+
+
+ +filter{banners-by-link} # Kill banners by their links to known clicktrackers
+
+
+ +filter{webbugs} # Squish WebBugs (1x1 invisible GIFs used for user tracking)
+
+
+ +filter{tiny-textforms} # Extend those tiny textareas up to 40x80 and kill the hard wrap
+
+
+ +filter{jumping-windows} # Prevent windows from resizing and moving themselves
+
+
+ +filter{frameset-borders} # Give frames a border and make them resizable
+
+
+ +filter{demoronizer} # Fix MS's non-standard use of standard charsets
+
+
+ +filter{shockwave-flash} # Kill embedded Shockwave Flash objects
+
+
+ +filter{quicktime-kioskmode} # Make Quicktime movies saveable
+
+
+ +filter{fun} # Text replacements for subversive browsing fun!
+
+
+ +filter{crude-parental} # Crude parental filtering (demo only)
+
+
+ +filter{ie-exploits} # Disable some known Internet Explorer bug exploits
+
+
+-------------------------------------------------------------------------------
+
+8.5.9. handle-as-image
+
+Typical use:
+
+ Mark URLs as belonging to images (so they'll be replaced by images if they
+ get blocked)
+
+Effect:
+
+ This action alone doesn't do anything noticeable. It just marks URLs as
+ images. If the block action also applies, the presence or absence of this
+ mark decides whether an HTML "blocked" page, or a replacement image (as
+ determined by the set-image-blocker action) will be sent to the client as a
+ substitute for the blocked content.
+
+Type:
+
+ Boolean.
+
+Parameter:
+
+ N/A
+
+Notes:
+
+ The below generic example section is actually part of default.action. It
+ marks all URLs with well-known image file name extensions as images and
+ should be left intact.
+
+ Users will probably only want to use the handle-as-image action in
+ conjunction with block, to block sources of banners, whose URLs don't
+ reflect the file type, like in the second example section.
+
+ Note that you cannot treat HTML pages as images in most cases. For
+ instance, (in-line) ad frames require an HTML page to be sent, or they
+ won't display properly. Forcing handle-as-image in this situation will not
+ replace the ad frame with an image, but lead to error messages.
+
+Example usage (sections):
+
+ # Generic image extensions:
+ #
+ {+handle-as-image}
+ /.*\.(gif|jpg|jpeg|png|bmp|ico)$
+
+ # These don't look like images, but they're banners and should be
+ # blocked as images:
+ #
+ {+block +handle-as-image}
+ some.nasty-banner-server.com/junk.cgi?output=trash
+
+ # Banner source! Who cares if they also have non-image content?
+ ad.doubleclick.net
+
+
+-------------------------------------------------------------------------------
+
+8.5.10. hide-forwarded-for-headers
+
+Typical use:
+
+ Improve privacy by hiding the true source of the request
+
+Effect:
+
+ Deletes any existing "X-Forwarded-for:" HTTP header from client requests,
+ and prevents adding a new one.
+
+Type:
+
+ Boolean.
+
+Parameter:
+
+ N/A
+
+Notes:
+
+ It is fairly safe to leave this on.
+
+ This action is scheduled for improvement: It should be able to generate
+ forged "X-Forwarded-for:" headers using random IP addresses from a
+ specified network, to make successive requests from the same client look
+ like requests from a pool of different users sharing the same proxy.
+
+Example usage:
+
+ +hide-forwarded-for-headers
+
+
+-------------------------------------------------------------------------------
+
+8.5.11. hide-from-header
+
+Typical use:
+
+ Keep your (old and ill) browser from telling web servers your email address
+
+Effect:
+
+ Deletes any existing "From:" HTTP header, or replaces it with the specified
+ string.
+
+Type:
+
+ Parameterized.
+
+Parameter:
+
+ Keyword: "block", or any user defined value.
+
+Notes:
+
+ The keyword "block" will completely remove the header (not to be confused
+ with the block action).
+
+ Alternately, you can specify any value you prefer to be sent to the web
+ server. If you do, it is a matter of fairness not to use any address that
+ is actually used by a real person.
+
+ This action is rarely needed, as modern web browsers don't send "From:"
+ headers anymore.
+
+Example usage:
+
+ +hide-from-header{block}
+
+
+ or
+
+ +hide-from-header{spam-me-senseless@sittingduck.example.com}
+
+
+-------------------------------------------------------------------------------
+
+8.5.12. hide-referrer
+
+Typical use:
+
+ Conceal which link you followed to get to a particular site
+
+Effect:
+
+ Deletes the "Referer:" (sic) HTTP header from the client request, or
+ replaces it with a forged one.
+
+Type:
+
+ Parameterized.
+
+Parameter:
+
+ + "block" to delete the header completely.
+
+ + "forge" to pretend to be coming from the homepage of the server we are
+ talking to.
+
+ + Any other string to set a user defined referrer.
+
+Notes:
+
+ "forge" is the preferred option here, since some servers will not send
+ images back otherwise, in an attempt to prevent their valuable content from
+ being embedded elsewhere (and hence, without being surrounded by their
+ banners).
+
+ hide-referer is an alternate spelling of hide-referrer and the two can be
+ can be freely substituted with each other. ("referrer" is the correct
+ English spelling, however the HTTP specification has a bug - it requires it
+ to be spelled as "referer".)
+
+Example usage:
+
+ +hide-referrer{forge}
+
+
+ or
+
+ +hide-referrer{http://www.yahoo.com/}
+
+
+-------------------------------------------------------------------------------
+
+8.5.13. hide-user-agent
+
+Typical use:
+
+ Conceal your type of browser and client operating system
+
+Effect:
+
+ Replaces the value of the "User-Agent:" HTTP header in client requests with
+ the specified value.
+
+Type:
+
+ Parameterized.
+
+Parameter:
+
+ Any user-defined string.
+
+Notes:
+
+ +-----------------------------------------------------------------+
+ | Warning |
+ |-----------------------------------------------------------------|
+ |This breaks many web sites that depend on looking at this header |
+ |in order to customize their content for different browsers |
+ |(which, by the way, is NOT a smart way to do that!). |
+ +-----------------------------------------------------------------+
+
+ Using this action in multi-user setups or wherever different types of
+ browsers will access the same Privoxy is not recommended. In single-user,
+ single-browser setups, you might use it to delete your OS version
+ information from the headers, because it is an invitation to exploit known
+ bugs for your OS. It is also occasionally useful to forge this in order to
+ access sites that won't let you in otherwise (though there may be a good
+ reason in some cases). Example of this: some MSN sites will not let Mozilla
+ enter, yet forging to a Netscape 6.1 user-agent works just fine. (Must be
+ just a silly MS goof, I'm sure :-).
+
+ This action is scheduled for improvement.
+
+Example usage:
+
+ +hide-user-agent{Netscape 6.1 (X11; I; Linux 2.4.18 i686)}
+
+
+-------------------------------------------------------------------------------
+
+8.5.14. kill-popups
+
+Typical use:
+
+ Eliminate those annoying pop-up windows (deprecated)
+
+Effect:
+
+ While loading the document, replace JavaScript code that opens pop-up
+ windows with (syntactically neutral) dummy code on the fly.
+
+Type:
+
+ Boolean.
+
+Parameter:
+
+ N/A
+
+Notes:
+
+ This action is basically a built-in, hardwired special-purpose filter
+ action, but there are important differences: For kill-popups, the document
+ need not be buffered, so it can be incrementally rendered while
+ downloading. But kill-popups doesn't catch as many pop-ups as filter
+ {all-popups} does and is not as smart as filter{unsolicited-popups} is.
+
+ Think of it as a fast and efficient replacement for a filter that you can
+ use if you don't want any filtering at all. Note that it doesn't make sense
+ to combine it with any filter action, since as soon as one filter applies,
+ the whole document needs to be buffered anyway, which destroys the
+ advantage of the kill-popups action over its filter equivalent.
+
+ Killing all pop-ups unconditionally is problematic. Many shops and banks
+ rely on pop-ups to display forms, shopping carts etc, and the filter
+ {unsolicited-popups} does a fairly good job of catching only the unwanted
+ ones.
+
+ If the only kind of pop-ups that you want to kill are exit consoles (those
+ really nasty windows that appear when you close an other one), you might
+ want to use filter{js-annoyances} instead.
+
+Example usage:
+
+ +kill-popups
+
+
+-------------------------------------------------------------------------------
+
+8.5.15. limit-connect
+
+Typical use:
+
+ Prevent abuse of Privoxy as a TCP proxy relay
+
+Effect:
+
+ Specifies to which ports HTTP CONNECT requests are allowable.
+
+Type:
+
+ Parameterized.
+
+Parameter:
+
+ A comma-separated list of ports or port ranges (the latter using dashes,
+ with the minimum defaulting to 0 and the maximum to 65K).
+
+Notes:
+
+ By default, i.e. if no limit-connect action applies, Privoxy only allows
+ HTTP CONNECT requests to port 443 (the standard, secure HTTPS port). Use
+ limit-connect if more fine-grained control is desired for some or all
+ destinations.
+
+ The CONNECT methods exists in HTTP to allow access to secure websites
+ ("https://" URLs) through proxies. It works very simply: the proxy connects
+ to the server on the specified port, and then short-circuits its
+ connections to the client and to the remote server. This can be a big
+ security hole, since CONNECT-enabled proxies can be abused as TCP relays
+ very easily.
+
+ If you don't know what any of this means, there probably is no reason to
+ change this one, since the default is already very restrictive.
+
+Example usages:
+
+ +limit-connect{443} # This is the default and need not be specified.
+ +limit-connect{80,443} # Ports 80 and 443 are OK.
+ +limit-connect{-3, 7, 20-100, 500-} # Ports less than 3, 7, 20 to 100 and above 500 are OK.
+ +limit-connect{-} # All ports are OK (gaping security hole!)
+
+
+-------------------------------------------------------------------------------
+
+8.5.16. prevent-compression
+
+Typical use:
+
+ Ensure that servers send the content uncompressed, so it can be passed
+ through filters
+
+Effect:
+
+ Adds a header to the request that asks for uncompressed transfer.
+
+Type:
+
+ Boolean.
+
+Parameter:
+
+ N/A
+
+Notes:
+
+ More and more websites send their content compressed by default, which is
+ generally a good idea and saves bandwidth. But for the filter,
+ deanimate-gifs and kill-popups actions to work, Privoxy needs access to the
+ uncompressed data. Unfortunately, Privoxy can't yet(!) uncompress, filter,
+ and re-compress the content on the fly. So if you want to ensure that all
+ websites, including those that normally compress, can be filtered, you need
+ to use this action.
+
+ This will slow down transfers from those websites, though. If you use any
+ of the above-mentioned actions, you will typically want to use
+ prevent-compression in conjunction with them.
+
+ Note that some (rare) ill-configured sites don't handle requests for
+ uncompressed documents correctly (they send an empty document body). If you
+ use prevent-compression per default, you'll have to add exceptions for
+ those sites. See the example for how to do that.
+
+Example usage (sections):
+
+ # Set default:
+ #
+ {+prevent-compression}
+ / # Match all sites
+
+ # Make exceptions for ill sites:
+ #
+ {-prevent-compression}
+ www.debianhelp.org
+ www.pclinuxonline.com
+
+
+-------------------------------------------------------------------------------
+
+8.5.17. send-vanilla-wafer
+
+Typical use:
+
+ Feed log analysis scripts with useless data.
+
+Effect:
+
+ Sends a cookie with each request stating that you do not accept any
+ copyright on cookies sent to you, and asking the site operator not to track
+ you.
+
+Type:
+
+ Boolean.
+
+Parameter:
+
+ N/A
+
+Notes:
+
+ The vanilla wafer is a (relatively) unique header and could conceivably be
+ used to track you.
+
+ This action is rarely used and not enabled in the default configuration.
+
+Example usage:
+
+ +send-vanilla-wafer
+
+
+-------------------------------------------------------------------------------
+
+8.5.18. send-wafer
+
+Typical use:
+
+ Send custom cookies or feed log analysis scripts with even more useless
+ data.
+
+Effect:
+
+ Sends a custom, user-defined cookie with each request.
+
+Type:
+
+ Multi-value.
+
+Parameter:
+
+ A string of the form "name=value".
+
+Notes:
+
+ Being multi-valued, multiple instances of this action can apply to the same
+ request, resulting in multiple cookies being sent.
+
+ This action is rarely used and not enabled in the default configuration.
+
+Example usage (section):
+
+ {+send-wafer{UsingPrivoxy=true}}
+ my-internal-testing-server.void
+
+
+-------------------------------------------------------------------------------
+
+8.5.19. session-cookies-only
+
+Typical use:
+
+ Allow only temporary "session" cookies (for the current browser session
+ only).
+
+Effect:
+
+ Deletes the "expires" field from "Set-Cookie:" server headers. Most
+ browsers will not store such cookies permanently and forget them in between
+ sessions.
+
+Type:
+
+ Boolean.
+
+Parameter:
+
+ N/A
+
+Notes:
+
+ This is less strict than crunch-incoming-cookies / crunch-outgoing-cookies
+ and allows you to browse websites that insist or rely on setting cookies,
+ without compromising your privacy too badly.
+
+ Most browsers will not permanently store cookies that have been processed
+ by session-cookies-only and will forget about them between sessions. This
+ makes profiling cookies useless, but won't break sites which require
+ cookies so that you can log in for transactions. This is generally turned
+ on for all sites, and is the recommended setting.
+
+ It makes no sense at all to use session-cookies-only together with
+ crunch-incoming-cookies or crunch-outgoing-cookies. If you do, cookies will
+ be plainly killed.
+
+ Note that it is up to the browser how it handles such cookies without an
+ "expires" field. If you use an exotic browser, you might want to try it out
+ to be sure.
+
+ This setting also has no effect on cookies that may have been stored
+ previously by the browser before starting Privoxy. These would have to be
+ removed manually.
+
+ Privoxy also uses the content-cookies filter to block some types of
+ cookies. Content cookies are not effected by session-cookies-only.
+
+Example usage:
+
+ +session-cookies-only
+
+
+-------------------------------------------------------------------------------
+
+8.5.20. set-image-blocker
+
+Typical use:
+
+ Choose the replacement for blocked images
+
+Effect:
+
+ This action alone doesn't do anything noticeable. If both block and
+ handle-as-image also apply, i.e. if the request is to be blocked as an
+ image, then the parameter of this action decides what will be sent as a
+ replacement.
+
+Type:
+
+ Parameterized.
+
+Parameter:
+
+ + "pattern" to send a built-in checkerboard pattern image. The image is
+ visually decent, scales very well, and makes it obvious where banners
+ were busted.
+
+ + "blank" to send a built-in transparent image. This makes banners
+ disappear completely, but makes it hard to detect where Privoxy has
+ blocked images on a given page and complicates troubleshooting if
+ Privoxy has blocked innocent images, like navigation icons.
+
+ + "target-url" to send a redirect to target-url. You can redirect to any
+ image anywhere, even in your local filesystem (via "file:///" URL).
+
+ A good application of redirects is to use special Privoxy-built-in
+ URLs, which send the built-in images, as target-url. This has the same
+ visual effect as specifying "blank" or "pattern" in the first place,
+ but enables your browser to cache the replacement image, instead of
+ requesting it over and over again.
+
+Notes:
+
+ The URLs for the built-in images are "http://config.privoxy.org/
+ send-banner?type=type", where type is either "blank" or "pattern".
+
+ There is a third (advanced) type, called "auto". It is NOT to be used in
+ set-image-blocker, but meant for use from filters. Auto will select the
+ type of image that would have applied to the referring page, had it been an
+ image.
+
+Example usage:
+
+ Built-in pattern:
+
+ +set-image-blocker{pattern}
+
+
+ Redirect to the BSD devil:
+
+ +set-image-blocker{http://www.freebsd.org/gifs/dae_up3.gif}
+
+
+ Redirect to the built-in pattern for better caching:
+
+ +set-image-blocker{http://config.privoxy.org/send-banner?type=pattern}
+
+
+-------------------------------------------------------------------------------
+
+8.5.21. Summary
+
+Note that many of these actions have the potential to cause a page to
+misbehave, possibly even not to display at all. There are many ways a site
+designer may choose to design his site, and what HTTP header content, and other
+criteria, he may depend on. There is no way to have hard and fast rules for all
+sites. See the Appendix for a brief example on troubleshooting actions.
+
+-------------------------------------------------------------------------------
+
+8.6. Aliases
+
+Custom "actions", known to Privoxy as "aliases", can be defined by combining
+other actions. These can in turn be invoked just like the built-in actions.
+Currently, an alias name can contain any character except space, tab, "=", "{"
+and "}", but we strongly recommend that you only use "a" to "z", "0" to "9",
+"+", and "-". Alias names are not case sensitive, and are not required to start
+with a "+" or "-" sign, since they are merely textually expanded.
+
+Aliases can be used throughout the actions file, but they must be defined in a
+special section at the top of the file! And there can only be one such section
+per actions file. Each actions file may have its own alias section, and the
+aliases defined in it are only visible within that file.
+
+There are two main reasons to use aliases: One is to save typing for frequently
+used combinations of actions, the other one is a gain in flexibility: If you
+decide once how you want to handle shops by defining an alias called "shop",
+you can later change your policy on shops in one place, and your changes will
+take effect everywhere in the actions file where the "shop" alias is used.
+Calling aliases by their purpose also makes your actions files more readable.
+
+Currently, there is one big drawback to using aliases, though: Privoxy's
+built-in web-based action file editor honors aliases when reading the actions
+files, but it expands them before writing. So the effects of your aliases are
+of course preserved, but the aliases themselves are lost when you edit sections
+that use aliases with it. This is likely to change in future versions of
+Privoxy.
+
+Now let's define some aliases...
+
+ # Useful custom aliases we can use later.
+ #
+ # Note the (required!) section header line and that this section
+ # must be at the top of the actions file!
+ #
+ {{alias}}
+
+ # These aliases just save typing later:
+ # (Note that some already use other aliases!)
+ #
+ +crunch-all-cookies = +crunch-incoming-cookies +crunch-outgoing-cookies
+ -crunch-all-cookies = -crunch-incoming-cookies -crunch-outgoing-cookies
+ block-as-image = +block +handle-as-image
+ mercy-for-cookies = -crunch-all-cookies -session-cookies-only -filter{content-cookies}
+
+ # These aliases define combinations of actions
+ # that are useful for certain types of sites:
+ #
+ fragile = -block -filter -crunch-all-cookies -fast-redirects -hide-referrer -kill-popups
+ shop = -crunch-all-cookies -filter{all-popups} -kill-popups
+
+ # Short names for other aliases, for really lazy people ;-)
+ #
+ c0 = +crunch-all-cookies
+ c1 = -crunch-all-cookies
+
+
+...and put them to use. These sections would appear in the lower part of an
+actions file and define exceptions to the default actions (as specified further
+up for the "/" pattern):
+
+ # These sites are either very complex or very keen on
+ # user data and require minimal interference to work:
+ #
+ {fragile}
+ .office.microsoft.com
+ .windowsupdate.microsoft.com
+ .nytimes.com
+
+ # Shopping sites:
+ # Allow cookies (for setting and retrieving your customer data)
+ #
+ {shop}
+ .quietpc.com
+ .worldpay.com # for quietpc.com
+ .scan.co.uk
+
+ # These shops require pop-ups:
+ #
+ {shop -kill-popups -filter{all-popups}}
+ .dabs.com
+ .overclockers.co.uk
+
+
+Aliases like "shop" and "fragile" are often used for "problem" sites that
+require some actions to be disabled in order to function properly.
+
+-------------------------------------------------------------------------------
+
+8.7. Actions Files Tutorial
+
+The above chapters have shown which actions files there are and how they are
+organized, how actions are specified and applied to URLs, how patterns work,
+and how to define and use aliases. Now, let's look at an example default.action
+and user.action file and see how all these pieces come together:
+
+-------------------------------------------------------------------------------
+
+8.7.1. default.action
+
+Every config file should start with a short comment stating its purpose:
+
+# Sample default.action file <developers@privoxy.org>
+
+
+Then, since this is the default.action file, the first section is a special
+section for internal use that you needn't change or worry about:
+
+##########################################################################
+# Settings -- Don't change! For internal Privoxy use ONLY.
+##########################################################################
+
+{{settings}}
+for-privoxy-version=3.0
+
+
+After that comes the (optional) alias section. We'll use the example section
+from the above chapter on aliases, that also explains why and how aliases are
+used:
+
+##########################################################################
+# Aliases
+##########################################################################
+{{alias}}
+
+ # These aliases just save typing later:
+ # (Note that some already use other aliases!)
+ #
+ +crunch-all-cookies = +crunch-incoming-cookies +crunch-outgoing-cookies
+ -crunch-all-cookies = -crunch-incoming-cookies -crunch-outgoing-cookies
+ block-as-image = +block +handle-as-image
+ mercy-for-cookies = -crunch-all-cookies -session-cookies-only -filter{content-cookies}
+
+ # These aliases define combinations of actions
+ # that are useful for certain types of sites:
+ #
+ fragile = -block -filter -crunch-all-cookies -fast-redirects -hide-referrer -kill-popups
+ shop = -crunch-all-cookies -filter{all-popups} -kill-popups
+
+
+Now come the regular sections, i.e. sets of actions, accompanied by URL
+patterns to which they apply. Remember all actions are disabled when matching
+starts, so we have to explicitly enable the ones we want.
+
+The first regular section is probably the most important. It has only one
+pattern, "/", but this pattern matches all URLs. Therefore, the set of actions
+used in this "default" section will be applied to all requests as a start. It
+can be partly or wholly overridden by later matches further down this file, or
+in user.action, but it will still be largely responsible for your overall
+browsing experience.
+
+Again, at the start of matching, all actions are disabled, so there is no real
+need to disable any actions here, but we will do that nonetheless, to have a
+complete listing for your reference. (Remember: a "+" preceding the action name
+enables the action, a "-" disables!). Also note how this long line has been
+made more readable by splitting it into multiple lines with line continuation.
+
+##########################################################################
+# "Defaults" section:
+##########################################################################
+ { \
+ -add-header \
+ -block \
+ -crunch-incoming-cookies \
+ -crunch-outgoing-cookies \
+ +deanimate-gifs \
+ -downgrade-http-version \
+ +fast-redirects \
+ +filter{js-annoyances} \
+ -filter{js-events} \
+ +filter{html-annoyances} \
+ -filter{content-cookies} \
+ +filter{refresh-tags} \
+ +filter{unsolicited-popups} \
+ -filter{all-popups} \
+ +filter{img-reorder} \
+ +filter{banners-by-size} \
+ -filter{banners-by-link} \
+ +filter{webbugs} \
+ -filter{tiny-textforms} \
+ +filter{jumping-windows} \
+ -filter{frameset-borders} \
+ -filter{demoronizer} \
+ -filter{shockwave-flash} \
+ -filter{quicktime-kioskmode} \
+ -filter{fun} \
+ -filter{crude-parental} \
+ +filter{ie-exploits} \
+ -handle-as-image \
+ +hide-forwarded-for-headers \
+ +hide-from-header{block} \
+ +hide-referrer{forge} \
+ -hide-user-agent \
+ -kill-popups \
+ -limit-connect \
+ +prevent-compression \
+ -send-vanilla-wafer \
+ -send-wafer \
+ +session-cookies-only \
+ +set-image-blocker{pattern} \
+ }
+ / # forward slash will match *all* potential URL patterns.
+
+
+The default behavior is now set. Note that some actions, like not hiding the
+user agent, are part of a "general policy" that applies universally and won't
+get any exceptions defined later. Other choices, like not blocking (which is
+understandably the default!) need exceptions, i.e. we need to specify
+explicitly what we want to block in later sections.
+
+The first of our specialized sections is concerned with "fragile" sites, i.e.
+sites that require minimum interference, because they are either very complex
+or very keen on tracking you (and have mechanisms in place that make them
+unusable for people who avoid being tracked). We will simply use our
+pre-defined fragile alias instead of stating the list of actions explicitly:
+
+##########################################################################
+# Exceptions for sites that'll break under the default action set:
+##########################################################################
+
+# "Fragile" Use a minimum set of actions for these sites (see alias above):
+#
+{ fragile }
+.office.microsoft.com # surprise, surprise!
+.windowsupdate.microsoft.com
+
+
+Shopping sites are not as fragile, but they typically require cookies to log
+in, and pop-up windows for shopping carts or item details. Again, we'll use a
+pre-defined alias:
+
+# Shopping sites:
+#
+{ shop }
+.quietpc.com
+.worldpay.com # for quietpc.com
+.jungle.com
+.scan.co.uk
+
+
+The fast-redirects action, which we enabled per default above, breaks some
+sites. So disable it for popular sites where we know it misbehaves:
+
+{ -fast-redirects }
+login.yahoo.com
+edit.*.yahoo.com
+.google.com
+.altavista.com/.*(like|url|link):http
+.altavista.com/trans.*urltext=http
+.nytimes.com
+
+
+It is important that Privoxy knows which URLs belong to images, so that if they
+are to be blocked, a substitute image can be sent, rather than an HTML page.
+Contacting the remote site to find out is not an option, since it would destroy
+the loading time advantage of banner blocking, and it would feed the
+advertisers (in terms of money and information). We can mark any URL as an
+image with the handle-as-image action, and marking all URLs that end in a known
+image file extension is a good start:
+
+##########################################################################
+# Images:
+##########################################################################
+
+# Define which file types will be treated as images, in case they get
+# blocked further down this file:
+#
+{ +handle-as-image }
+/.*\.(gif|jpe?g|png|bmp|ico)$
+
+
+And then there are known banner sources. They often use scripts to generate the
+banners, so it won't be visible from the URL that the request is for an image.
+Hence we block them and mark them as images in one go, with the help of our
+block-as-image alias defined above. (We could of course just as well use +block
++handle-as-image here.) Remember that the type of the replacement image is
+chosen by the set-image-blocker action. Since all URLs have matched the default
+section with its +set-image-blocker{pattern} action before, it still applies
+and needn't be repeated:
+
+# Known ad generators:
+#
+{ block-as-image }
+ar.atwola.com
+.ad.doubleclick.net
+.ad.*.doubleclick.net
+.a.yimg.com/(?:(?!/i/).)*$
+.a[0-9].yimg.com/(?:(?!/i/).)*$
+bs*.gsanet.com
+bs*.einets.com
+.qkimg.net
+
+
+One of the most important jobs of Privoxy is to block banners. A huge bunch of
+them are already "blocked" by the filter{banners-by-size} action, which we
+enabled above, and which deletes the references to banner images from the pages
+while they are loaded, so the browser doesn't request them anymore, and hence
+they don't need to be blocked here. But this naturally doesn't catch all
+banners, and some people choose not to use filters, so we need a comprehensive
+list of patterns for banner URLs here, and apply the block action to them.
+
+First comes a bunch of generic patterns, which do most of the work, by matching
+typical domain and path name components of banners. Then comes a list of
+individual patterns for specific sites, which is omitted here to keep the
+example short:
+
+##########################################################################
+# Block these fine banners:
+##########################################################################
+{ +block }
+
+# Generic patterns:
+#
+ad*.
+.*ads.
+banner?.
+count*.
+/.*count(er)?\.(pl|cgi|exe|dll|asp|php[34]?)
+/(?:.*/)?(publicite|werbung|rekla(ma|me|am)|annonse|maino(kset|nta|s)?)/
+
+# Site-specific patterns (abbreviated):
+#
+.hitbox.com
+
+
+You wouldn't believe how many advertisers actually call their banner servers
+ads.company.com, or call the directory in which the banners are stored simply
+"banners". So the above generic patterns are surprisingly effective.
+
+But being very generic, they necessarily also catch URLs that we don't want to
+block. The pattern .*ads. e.g. catches "nasty-ads.nasty-corp.com" as intended,
+but also "downloads.sourcefroge.net" or "adsl.some-provider.net." So here come
+some well-known exceptions to the +block section above.
+
+Note that these are exceptions to exceptions from the default! Consider the URL
+"downloads.sourcefroge.net": Initially, all actions are deactivated, so it
+wouldn't get blocked. Then comes the defaults section, which matches the URL,
+but just deactivates the block action once again. Then it matches .*ads., an
+exception to the general non-blocking policy, and suddenly +block applies. And
+now, it'll match .*loads., where -block applies, so (unless it matches again
+further down) it ends up with no block action applying.
+
+##########################################################################
+# Save some innocent victims of the above generic block patterns:
+##########################################################################
+
+# By domain:
+#
+{ -block }
+adv[io]*. # (for advogato.org and advice.*)
+adsl. # (has nothing to do with ads)
+ad[ud]*. # (adult.* and add.*)
+.edu # (universities don't host banners (yet!))
+.*loads. # (downloads, uploads etc)
+
+# By path:
+#
+/.*loads/
+
+# Site-specific:
+#
+www.globalintersec.com/adv # (adv = advanced)
+www.ugu.com/sui/ugu/adv
+
+
+Filtering source code can have nasty side effects, so make an exception for our
+friends at sourceforge.net, and all paths with "cvs" in them. Note that -filter
+disables all filters in one fell swoop!
+
+# Don't filter code!
+#
+{ -filter }
+/.*cvs
+.sourceforge.net
+
+
+The actual default.action is of course more comprehensive, but we hope this
+example made clear how it works.
+
+-------------------------------------------------------------------------------
+
+8.7.2. user.action
+
+So far we are painting with a broad brush by setting general policies, which
+would be a reasonable starting point for many people. Now, you might want to be
+more specific and have customized rules that are more suitable to your personal
+habits and preferences. These would be for narrowly defined situations like
+your ISP or your bank, and should be placed in user.action, which is parsed
+after all other actions files and hence has the last word, over-riding any
+previously defined actions. user.action is also a safe place for your personal
+settings, since default.action is actively maintained by the Privoxy developers
+and you'll probably want to install updated versions from time to time.
+
+So let's look at a few examples of things that one might typically do in
+user.action:
+
+# My user.action file. <fred@foobar.com>
+
+
+As aliases are local to the actions file that they are defined in, you can't
+use the ones from default.action, unless you repeat them here:
+
+# Aliases are local to the file they are defined in.
+# (Re-)define aliases for this file:
+#
+{{alias}}
+#
+# These aliases just save typing later, and the alias names should
+# be self explanatory.
+#
++crunch-all-cookies = +crunch-incoming-cookies +crunch-outgoing-cookies
+-crunch-all-cookies = -crunch-incoming-cookies -crunch-outgoing-cookies
+ allow-all-cookies = -crunch-all-cookies -session-cookies-only
+ allow-popups = -filter{all-popups} -kill-popups
++block-as-image = +block +handle-as-image
+-block-as-image = -block
+
+# These aliases define combinations of actions that are useful for
+# certain types of sites:
+#
+fragile = -block -crunch-all-cookies -filter -fast-redirects -hide-referrer -kill-popups
+shop = -crunch-all-cookies allow-popups
+
+# Allow ads for selected useful free sites:
+#
+allow-ads = -block -filter{banners-by-size} -filter{banners-by-link}
+
+
+Say you have accounts on some sites that you visit regularly, and you don't
+want to have to log in manually each time. So you'd like to allow persistent
+cookies for these sites. The allow-all-cookies alias defined above does exactly
+that, i.e. it disables crunching of cookies in any direction, and the
+processing of cookies to make them only temporary.
+
+{ allow-all-cookies }
+sourceforge.net
+sunsolve.sun.com
+.slashdot.org
+.yahoo.com
+.msdn.microsoft.com
+.redhat.com
+
+
+Your bank is allergic to some filter, but you don't know which, so you disable
+them all:
+
+{ -filter }
+.your-home-banking-site.com
+
+
+Some file types you may not want to filter for various reasons:
+
+# Technical documentation is likely to contain strings that might
+# erroneously get altered by the JavaScript-oriented filters:
+#
+.tldp.org
+/(.*/)?selfhtml/
+
+# And this stupid host sends streaming video with a wrong MIME type,
+# so that Privoxy thinks it is getting HTML and starts filtering:
+#
+stupid-server.example.com/
+
+
+Example of a simple block action. Say you've seen an ad on your favourite page
+on example.com that you want to get rid of. You have right-clicked the image,
+selected "copy image location" and pasted the URL below while removing the
+leading http://, into a { +block } section. Note that { +handle-as-image } need
+not be specified, since all URLs ending in .gif will be tagged as images by the
+general rules as set in default.action anyway:
+
+{ +block }
+www.example.com/nasty-ads/sponsor.gif
+another.popular.site.net/more/junk/here/
+
+
+The URLs of dynamically generated banners, especially from large banner farms,
+often don't use the well-known image file name extensions, which makes it
+impossible for Privoxy to guess the file type just by looking at the URL. You
+can use the +block-as-image alias defined above for these cases. Note that
+objects which match this rule but then turn out NOT to be an image are
+typically rendered as a "broken image" icon by the browser. Use cautiously.
+
+{ +block-as-image }
+.doubleclick.net
+/Realmedia/ads/
+ar.atwola.com/
+
+
+Now you noticed that the default configuration breaks Forbes Magazine, but you
+were too lazy to find out which action is the culprit, and you were again too
+lazy to give feedback, so you just used the fragile alias on the site, and --
+whoa! -- it worked. The fragile aliases disables those actions that are most
+likely to break a site. Also, good for testing purposes to see if it is Privoxy
+that is causing the problem or not.
+
+{ fragile }
+.forbes.com
+
+
+You like the "fun" text replacements in default.filter, but it is disabled in
+the distributed actions file. (My colleagues on the team just don't have a
+sense of humour, that's why! ;-). So you'd like to turn it on in your private,
+update-safe config, once and for all:
+
+{ +filter{fun} }
+/ # For ALL sites!
+
+
+Note that the above is not really a good idea: There are exceptions to the
+filters in default.action for things that really shouldn't be filtered, like
+code on CVS->Web interfaces. Since user.action has the last word, these
+exceptions won't be valid for the "fun" filtering specified here.
+
+You might also worry about how your favourite free websites are funded, and
+find that they rely on displaying banner advertisements to survive. So you
+might want to specifically allow banners for those sites that you feel provide
+value to you:
+
+{ allow-ads }
+.sourceforge.net
+.slashdot.org
+.osdn.net
+
+
+Note that allow-ads has been aliased to -block, -filter{banners-by-size}, and -
+filter{banners-by-link} above.
+
+user.action is generally the best place to define exceptions and additions to
+the default policies of default.action. Some actions are safe to have their
+default policies set here though. So let's set a default policy to have a
+"blank" image as opposed to the checkerboard pattern for ALL sites. "/" of
+course matches all URL paths and patterns:
+
+{ +set-image-blocker{blank} }
+/ # ALL sites
+
+
+-------------------------------------------------------------------------------
+
+9. The Filter File
+
+All text substitutions that can be invoked through the filter action must first
+be defined in the filter file, which is typically called default.filter and
+which can be selected through the filterfile config option.
+
+Typical reasons for doing such substitutions are to eliminate common annoyances
+in HTML and JavaScript, such as pop-up windows, exit consoles, crippled windows
+without navigation tools, the infamous <BLINK> tag etc, to suppress images with
+certain width and height attributes (standard banner sizes or web-bugs), or
+just to have fun. The possibilities are endless.
+
+Filtering works on any text-based document type, including HTML, JavaScript,
+CSS etc. (all text/* MIME types, except text/plain). Substitutions are made at
+the source level, so if you want to "roll your own" filters, you should be
+familiar with HTML syntax.
+
+Just like the actions files, the filter file is organized in sections, which
+are called filters here. Each filter consists of a heading line, that starts
+with the keyword FILTER:, followed by the filter's name, and a short (one line)
+description of what it does. Below that line come the jobs, i.e. lines that
+define the actual text substitutions. By convention, the name of a filter
+should describe what the filter eliminates. The comment is used in the
+web-based user interface.
+
+Once a filter called name has been defined in the filter file, it can be
+invoked by using an action of the form +filter{name} in any actions file.
+
+A filter header line for a filter called "foo" could look like this:
+
+FILTER: foo Replace all "foo" with "bar"
+
+
+Below that line, and up to the next header line, come the jobs that define what
+text replacements the filter executes. They are specified in a syntax that
+imitates Perl's s/// operator. If you are familiar with Perl, you will find
+this to be quite intuitive, and may want to look at the PCRS man page for the
+subtle differences to Perl behaviour. Most notably, the non-standard option
+letter U is supported, which turns the default to ungreedy matching.
+
+If you are new to regular expressions, you might want to take a look at the
+Appendix on regular expressions, and see the Perl manual for the s///
+operator's syntax and Perl-style regular expressions in general. The below
+examples might also help to get you started.
+
+-------------------------------------------------------------------------------
+
+9.1. Filter File Tutorial
+
+Now, let's complete our "foo" filter. We have already defined the heading, but
+the jobs are still missing. Since all it does is to replace "foo" with "bar",
+there is only one (trivial) job needed:
+
+s/foo/bar/
+
+
+But wait! Didn't the comment say that all occurrences of "foo" should be
+replaced? Our current job will only take care of the first "foo" on each page.
+For global substitution, we'll need to add the g option:
+
+s/foo/bar/g
+
+
+Our complete filter now looks like this:
+
+FILTER: foo Replace all "foo" with "bar"
+s/foo/bar/g
+
+
+Let's look at some real filters for more interesting examples. Here you see a
+filter that protects against some common annoyances that arise from JavaScript
+abuse. Let's look at its jobs one after the other:
+
+FILTER: js-annoyances Get rid of particularly annoying JavaScript abuse
+
+# Get rid of JavaScript referrer tracking. Test page: http://www.randomoddness.com/untitled.htm
+#
+s|(<script.*)document\.referrer(.*</script>)|$1"Not Your Business!"$2|Usg
+
+
+Following the header line and a comment, you see the job. Note that it uses |
+as the delimiter instead of /, because the pattern contains a forward slash,
+which would otherwise have to be escaped by a backslash (\).
+
+Now, let's examine the pattern: it starts with the text <script.* enclosed in
+parentheses. Since the dot matches any character, and * means: "Match an
+arbitrary number of the element left of myself", this matches "<script",
+followed by any text, i.e. it matches the whole page, from the start of the
+first <script> tag.
+
+That's more than we want, but the pattern continues: document\.referrer matches
+only the exact string "document.referrer". The dot needed to be escaped, i.e.
+preceded by a backslash, to take away its special meaning as a joker, and make
+it just a regular dot. So far, the meaning is: Match from the start of the
+first <script> tag in a the page, up to, and including, the text
+"document.referrer", if both are present in the page (and appear in that
+order).
+
+But there's still more pattern to go. The next element, again enclosed in
+parentheses, is .*</script>. You already know what .* means, so the whole
+pattern translates to: Match from the start of the first <script> tag in a page
+to the end of the last <script> tag, provided that the text "document.referrer"
+appears somewhere in between.
+
+This is still not the whole story, since we have ignored the options and the
+parentheses: The portions of the page matched by sub-patterns that are enclosed
+in parentheses, will be remembered and be available through the variables $1,
+$2, ... in the substitute. The U option switches to ungreedy matching, which
+means that the first .* in the pattern will only "eat up" all text in between "
+<script" and the first occurrence of "document.referrer", and that the second
+.* will only span the text up to the first "</script>" tag. Furthermore, the s
+option says that the match may span multiple lines in the page, and the g
+option again means that the substitution is global.
+
+So, to summarize, the pattern means: Match all scripts that contain the text
+"document.referrer". Remember the parts of the script from (and including) the
+start tag up to (and excluding) the string "document.referrer" as $1, and the
+part following that string, up to and including the closing tag, as $2.
+
+Now the pattern is deciphered, but wasn't this about substituting things? So
+lets look at the substitute: $1"Not Your Business!"$2 is easy to read: The text
+remembered as $1, followed by "Not Your Business!" (including the quotation
+marks!), followed by the text remembered as $2. This produces an exact copy of
+the original string, with the middle part (the "document.referrer") replaced by
+"Not Your Business!".
+
+The whole job now reads: Replace "document.referrer" by "Not Your Business!"
+wherever it appears inside a <script> tag. Note that this job won't break
+JavaScript syntax, since both the original and the replacement are
+syntactically valid string objects. The script just won't have access to the
+referrer information anymore.
+
+We'll show you two other jobs from the JavaScript taming department, but this
+time only point out the constructs of special interest:
+
+# The status bar is for displaying link targets, not pointless blahblah
+#
+s/window\.status\s*=\s*(['"]).*?\1/dUmMy=1/ig
+
+
+\s stands for whitespace characters (space, tab, newline, carriage return, form
+feed), so that \s* means: "zero or more whitespace". The ? in .*? makes this
+matching of arbitrary text ungreedy. (Note that the U option is not set). The
+['"] construct means: "a single or a double quote". Finally, \1 is a
+backreference to the first parenthesis just like $1 above, with the difference
+that in the pattern, a backslash indicates a backreference, whereas in the
+substitute, it's the dollar.
+
+So what does this job do? It replaces assignments of single- or double-quoted
+strings to the "window.status" object with a dummy assignment (using a variable
+name that is hopefully odd enough not to conflict with real variables in
+scripts). Thus, it catches many cases where e.g. pointless descriptions are
+displayed in the status bar instead of the link target when you move your mouse
+over links.
+
+# Kill OnUnload popups. Yummy. Test: http://www.zdnet.com/zdsubs/yahoo/tree/yfs.html
+#
+s/(<body [^>]*)onunload(.*>)/$1never$2/iU
+
+
+Including the OnUnload event binding in the HTML DOM was a CRIME. When I close
+a browser window, I want it to close and die. Basta. This job replaces the
+"onunload" attribute in "<body>" tags with the dummy word never. Note that the
+i option makes the pattern matching case-insensitive. Also note that ungreedy
+matching alone doesn't always guarantee a minimal match: In the first
+parenthesis, we had to use [^>]* instead of .* to prevent the match from
+exceeding the <body> tag if it doesn't contain "OnUnload", but the page's
+content does.
+
+The last example is from the fun department:
+
+FILTER: fun Fun text replacements
+
+# Spice the daily news:
+#
+s/microsoft(?!\.com)/MicroSuck/ig
+
+
+Note the (?!\.com) part (a so-called negative lookahead) in the job's pattern,
+which means: Don't match, if the string ".com" appears directly following
+"microsoft" in the page. This prevents links to microsoft.com from being
+trashed, while still replacing the word everywhere else.
+
+# Buzzword Bingo (example for extended regex syntax)
+#
+s* industry[ -]leading \
+| cutting[ -]edge \
+| customer[ -]focused \
+| market[ -]driven \
+| award[ -]winning # Comments are OK, too! \
+| high[ -]performance \
+| solutions[ -]based \
+| unmatched \
+| unparalleled \
+| unrivalled \
+*<font color="red"><b>BINGO!</b></font> \
+*igx
+
+
+The x option in this job turns on extended syntax, and allows for e.g. the
+liberal use of (non-interpreted!) whitespace for nicer formatting.
+
+You get the idea?
+
+-------------------------------------------------------------------------------
+
+9.2. The Pre-defined Filters
+
+The distribution default.filter file contains a selection of pre-defined
+filters for your convenience:
+
+js-annoyances
+
+ The purpose of this filter is to get rid of particularly annoying
+ JavaScript abuse. To that end, it
+
+ + replaces JavaScript references to the browser's referrer information
+ with the string "Not Your Business!". This compliments the
+ hide-referrer action on the content level.
+
+ + removes the bindings to the DOM's unload event which we feel has no
+ right to exist and is responsible for most "exit consoles", i.e. nasty
+ windows that pop up when you close another one.
+
+ + removes code that causes new windows to be opened with undesired
+ properties, such as being full-screen, non-resizable, without location,
+ status or menu bar etc.
+
+js-events
+
+ This is a very radical measure. It removes virtually all JavaScript event
+ bindings, which means that scripts can not react to user actions such as
+ mouse movements or clicks, window resizing etc, anymore.
+
+ We strongly discourage using this filter as a default since it breaks many
+ legitimate scripts. It is meant for use only on extra-nasty sites (should
+ you really need to go there).
+
+html-annoyances
+
+ This filter will undo many common instances of HTML based abuse.
+
+ The BLINK and MARQUEE tags are neutralized (yeah baby!), and browser
+ windows will be created as resizable (as of course they should be!), and
+ will have location, scroll and menu bars -- even if specified otherwise.
+
+content-cookies
+
+ Most cookies are set in the HTTP dialogue, where they can be intercepted by
+ the crunch-incoming-cookies and crunch-outgoing-cookies actions. But web
+ sites increasingly make use of HTML meta tags and JavaScript to sneak
+ cookies to the browser on the content level.
+
+ This filter disables HTML and JavaScript code that reads or sets cookies.
+ Use it wherever you would also use the cookie crunch actions.
+
+refresh tags
+
+ Disable any refresh tags if the interval is greater than nine seconds (so
+ that redirections done via refresh tags are not destroyed). This is useful
+ for dial-on-demand setups, or for those who find this HTML feature
+ annoying.
+
+unsolicited-popups
+
+ This filter attempts to prevent only "unsolicited" pop-up windows from
+ opening, yet still allow pop-up windows that the user has explicitly chosen
+ to open. It was added in version 3.0.1, as an improvement over earlier such
+ filters.
+
+ Technical note: The filter works by redefining the window.open JavaScript
+ function to a dummy function during the loading and rendering phase of each
+ HTML page access, and restoring the function afterwards.
+
+all-popups
+
+ Attempt to prevent all pop-up windows from opening. Note this should be
+ used with more discretion than the above, since it is more likely to break
+ some sites that require pop-ups for normal usage. Use with caution.
+
+img-reorder
+
+ This is a helper filter that has no value if used alone. It makes the
+ banners-by-size and banners-by-link (see below) filters more effective and
+ should be enabled together with them.
+
+banners-by-size
+
+ This filter removes image tags purely based on what size they are.
+ Fortunately for us, many ads and banner images tend to conform to certain
+ standardized sizes, which makes this filter quite effective for ad
+ stripping purposes.
+
+ Occasionally this filter will cause false positives on images that are not
+ ads, but just happen to be of one of the standard banner sizes.
+
+banners-by-link
+
+ This is an experimental filter that attempts to kill any banners if their
+ URLs seem to point to known or suspected click trackers. It is currently
+ not of much value and is not recommended for use by default.
+
+webbugs
+
+ Webbugs are small, invisible images (technically 1X1 GIF images), that are
+ used to track users across websites, and collect information on them. As an
+ HTML page is loaded by the browser, an embedded image tag causes the
+ browser to contact a third-party site, disclosing the tracking information
+ through the requested URL and/or cookies for that third-party domain,
+ without the use ever becoming aware of the interaction with the third-party
+ site. HTML-ized spam also uses a similar technique to verify email
+ addresses.
+
+ This filter removes the HTML code that loads such "webbugs".
+
+tiny-textforms
+
+ A rather special-purpose filter that can be used to enlarge textareas
+ (those multi-line text boxes in web forms) and turn off hard word wrap in
+ them. It was written for the sourceforge.net tracker system where such
+ boxes are a nuisance, but it can be handy on other sites, too.
+
+ It is not recommended to use this filter as a default.
+
+jumping-windows
+
+ Many consider windows that move, or resize themselves to be abusive. This
+ filter neutralizes the related JavaScript code. Note that some sites might
+ not display or behave as intended when using this filter.
+
+frameset-borders
+
+ Some web designers seem to assume that everyone in the world will view
+ their web sites using the same browser brand and version, screen resolution
+ etc, because only that assumption could explain why they'd use static frame
+ sizes, yet prevent their frames from being resized by the user, should they
+ be too small to show their whole content.
+
+ This filter removes the related HTML code. It should only be applied to
+ sites which need it.
+
+demoronizer
+
+ Many Microsoft products that generate HTML use non-standard extensions
+ (read: violations) of the ISO 8859-1 aka Latin-1 character set. This causes
+ those HTML documents to display with errors on standard-compliant
+ platforms.
+
+ This filter translates the MS-only characters into Latin-1 equivalents. It
+ is not necessary when using MS products, and will cause corruption of all
+ documents that use 8-bit character sets other than Latin-1. It's mostly
+ worthwhile for Europeans on non-MS platforms, if wierd garbage characters
+ sometimes appear on some pages.
+
+shockwave-flash
+
+ A filter for shockwave haters. As the name suggests, this filter strips
+ code out of web pages that is used to embed shockwave flash objects.
+
+quicktime-kioskmode
+
+ Change HTML code that embeds Quicktime objects so that kioskmode, which
+ prevents saving, is disabled.
+
+fun
+
+ Text replacements for subversive browsing fun. Make fun of your favorite
+ Monopolist or play buzzword bingo.
+
+crude-parental
+
+ A demonstration-only filter that shows how Privoxy can be used to delete
+ web content on a keyword basis.
+
+ie-exploits
+
+ A collection of text replacements to disable malicious HTML and JavaScript
+ code that exploits known security holes in Internet Explorer.
+
+ Presently, it only protects against Nimda and a cross-site scripting bug,
+ and would need active maintenance to provide more substantial protection.
+
+site-specifics
+
+ Some web sites have very specific problems, the cure for which doesn't
+ apply anywhere else, or could even cause damage on other sites.
+
+ This is a collection of such site-specific cures which should only be
+ applied to the sites they were intended for, which is what the supplied
+ default.action file does. Users shouldn't need to change anything regarding
+ this filter.
+
+-------------------------------------------------------------------------------
+
+10. Templates
+
+All Privoxy built-in pages, i.e. error pages such as the "404 - No Such Domain"
+error page, the "BLOCKED" page and all pages of its web-based user interface,
+are generated from templates. (Privoxy must be running for the above links to
+work as intended.)