+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ Keyword: <quote>block</quote>, or any user defined value.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ Faking the browser's language settings can be useful to make a
+ foreign User-Agent set with
+ <literal><link linkend="hide-user-agent">hide-user-agent</link></literal>
+ more believable.
+ </para>
+ <para>
+ However some sites with content in different languages check the
+ <quote>Accept-Language:</quote> to decide which one to take by default.
+ Sometimes it isn't possible to later switch to another language without
+ changing the <quote>Accept-Language:</quote> header first.
+ </para>
+ <para>
+ Therefore it's a good idea to either only change the
+ <quote>Accept-Language:</quote> header to languages you understand,
+ or to languages that aren't wide spread.
+ </para>
+ <para>
+ Before setting the <quote>Accept-Language:</quote> header
+ to a rare language, you should consider that it helps to
+ make your requests unique and thus easier to trace.
+ If you don't plan to change this header frequently,
+ you should stick to a common language.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage (section):</term>
+ <listitem>
+ <para>
+ <screen># Pretend to use Canadian language settings.
+{+hide-accept-language{en-ca} \
++hide-user-agent{Mozilla/5.0 (X11; U; OpenBSD i386; en-CA; rv:1.8.0.4) Gecko/20060628 Firefox/1.5.0.4} \
+}
+/ </screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="hide-content-disposition">
+<title>hide-content-disposition</title>
+<!--
+new action
+-->
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Prevent download menus for content you prefer to view inside the browser.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Deletes or replaces the <quote>Content-Disposition:</quote> HTTP header set by some servers.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ Keyword: <quote>block</quote>, or any user defined value.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ Some servers set the <quote>Content-Disposition:</quote> HTTP header for
+ documents they assume you want to save locally before viewing them.
+ The <quote>Content-Disposition:</quote> header contains the file name
+ the browser is supposed to use by default.
+ </para>
+ <para>
+ In most browsers that understand this header, it makes it impossible to
+ <emphasis>just view</emphasis> the document, without downloading it first,
+ even if it's just a simple text file or an image.
+ </para>
+ <para>
+ Removing the <quote>Content-Disposition:</quote> header helps
+ to prevent this annoyance, but some browsers additionally check the
+ <quote>Content-Type:</quote> header, before they decide if they can
+ display a document without saving it first. In these cases, you have
+ to change this header as well, before the browser stops displaying
+ download menus.
+ </para>
+ <para>
+ It is also possible to change the server's file name suggestion
+ to another one, but in most cases it isn't worth the time to set
+ it up.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ <screen># Disarm the download link in Sourceforge's patch tracker
+{-filter\
++content-type-overwrite {text/plain}\
++hide-content-disposition {block} }
+.sourceforge.net/tracker/download.php</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="hide-if-modified-since">
+<title>hide-if-modified-since</title>
+<!--
+new action
+-->
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Prevent yet another way to track the user's steps between sessions.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Deletes the <quote>If-Modified-Since:</quote> HTTP client header or modifies its value.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ Keyword: <quote>block</quote>, or a user defined value that specifies a range of hours.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ Removing this header is useful for filter testing, where you want to force a real
+ reload instead of getting status code <quote>304</quote>, which would cause the
+ browser to use a cached copy of the page.
+ </para>
+ <para>
+ Instead of removing the header, <literal>hide-if-modified-since</literal> can
+ also add or subtract a random amount of time to/from the header's value.
+ You specify a range of minutes where the random factor should be chosen from and
+ <application>Privoxy</application> does the rest. A negative value means
+ subtracting, a positive value adding.
+ </para>
+ <para>
+ Randomizing the value of the <quote>If-Modified-Since:</quote> makes
+ sure it isn't used as a cookie replacement, but you will run into
+ caching problems if the random range is too high.
+ </para>
+ <para>
+ It is a good idea to only use a small negative value and let
+ <literal><link linkend="overwrite-last-modified">overwrite-last-modified</link></literal>
+ handle the greater changes.
+ </para>
+ <para>
+ It is also recommended to use this action together with
+ <literal><link linkend="crunch-if-none-match">crunch-if-none-match</link></literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage (section):</term>
+ <listitem>
+ <para>
+ <screen># Let the browser revalidate without being tracked across sessions
+{+hide-if-modified-since {-60}\
++overwrite-last-modified {randomize}\
++crunch-if-none-match}
+/</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="hide-forwarded-for-headers">
+<title>hide-forwarded-for-headers</title>
+<!--
+new action
+-->
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Improve privacy by hiding the true source of the request</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Deletes any existing <quote>X-Forwarded-for:</quote> HTTP header from client requests,
+ and prevents adding a new one.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Boolean.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ N/A
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ It is fairly safe to leave this on.
+ </para>
+ <para>
+ This action is scheduled for improvement: It should be able to generate forged
+ <quote>X-Forwarded-for:</quote> 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ <screen>+hide-forwarded-for-headers</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="hide-from-header">
+<title>hide-from-header</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Keep your (old and ill) browser from telling web servers your email address</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Deletes any existing <quote>From:</quote> HTTP header, or replaces it with the
+ specified string.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ Keyword: <quote>block</quote>, or any user defined value.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ The keyword <quote>block</quote> will completely remove the header
+ (not to be confused with the <literal><link linkend="block">block</link></literal>
+ action).
+ </para>
+ <para>
+ 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.
+ </para>
+ <para>
+ This action is rarely needed, as modern web browsers don't send
+ <quote>From:</quote> headers anymore.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ <screen>+hide-from-header{block}</screen> or
+ <screen>+hide-from-header{spam-me-senseless@sittingduck.example.com}</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="hide-referrer">
+<title>hide-referrer</title>
+<anchor id="hide-referer">
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Conceal which link you followed to get to a particular site</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Deletes the <quote>Referer:</quote> (sic) HTTP header from the client request,
+ or replaces it with a forged one.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <itemizedlist>
+ <listitem>
+ <para><quote>conditional-block</quote> to delete the header completely if the host has changed.</para>
+ </listitem>
+ <listitem>
+ <para><quote>block</quote> to delete the header unconditionally.</para>
+ </listitem>
+ <listitem>
+ <para><quote>forge</quote> to pretend to be coming from the homepage of the server we are talking to.</para>
+ </listitem>
+ <listitem>
+ <para>Any other string to set a user defined referrer.</para>
+ </listitem>
+ </itemizedlist>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ <literal>conditional-block</literal> is the only parameter,
+ that isn't easily detected in the server's log file. If it blocks the
+ referrer, the request will look like the visitor used a bookmark or
+ typed in the address directly.
+ </para>
+ <para>
+ Leaving the referrer unmodified for requests on the same host
+ allows the server owner to see the visitor's <quote>click path</quote>,
+ but in most cases she could also get that information by comparing
+ other parts of the log file: for example the User-Agent if it isn't
+ a very common one, or the user's IP address if it doesn't change between
+ different requests.
+ </para>
+ <para>
+ Always blocking the referrer, or using a custom one, can lead to
+ failures on servers that check the referrer before they answer any
+ requests, in an attempt to prevent their valuable content from being
+ embedded or linked to elsewhere.
+ </para>
+ <para>
+ Both <literal>conditional-block</literal> and <literal>forge</literal>
+ will work with referrer checks, as long as content and valid referring page
+ are on the same host. Most of the time that's the case.
+ </para>
+ <para>
+ <literal>hide-referer</literal> is an alternate spelling of
+ <literal>hide-referrer</literal> and the two can be can be freely
+ substituted with each other. (<quote>referrer</quote> is the
+ correct English spelling, however the HTTP specification has a bug - it
+ requires it to be spelled as <quote>referer</quote>.)
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ <screen>+hide-referrer{forge}</screen> or
+ <screen>+hide-referrer{http://www.yahoo.com/}</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="hide-user-agent">
+<title>hide-user-agent</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Conceal your type of browser and client operating system</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Replaces the value of the <quote>User-Agent:</quote> HTTP header
+ in client requests with the specified value.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ Any user-defined string.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <warning>
+ <para>
+ This can lead to problems on web sites that depend on looking at this header in
+ order to customize their content for different browsers (which, by the
+ way, is <emphasis>NOT</emphasis> the right thing to do: good web sites
+ work browser-independently).
+ <!--
+ <ulink url="http://www.javascriptkit.com/javaindex.shtml">smart way to do
+ that</ulink>!).
+ -->
+ </para>
+ </warning>
+ <para>
+ Using this action in multi-user setups or wherever different types of
+ browsers will access the same <application>Privoxy</application> is
+ <emphasis>not recommended</emphasis>. 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 <application>Mozilla</application> enter, yet forging to a
+ <application>Netscape 6.1</application> user-agent works just fine.
+ (Must be just a silly MS goof, I'm sure :-).
+ </para>
+ <para>
+ This action is scheduled for improvement.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ <screen>+hide-user-agent{Netscape 6.1 (X11; I; Linux 2.4.18 i686)}</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="inspect-jpegs">
+<title>inspect-jpegs</title>
+<!--
+new action
+-->
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>To protect against the MS buffer over-run in JPEG processing</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Protect against a known exploit
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Boolean.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ N/A
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ See Microsoft Security Bulletin MS04-028. JPEG images are one of the most
+ common image types found across the Internet. The exploit as described can
+ allow execution of code on the target system, giving an attacker access
+ to the system in question by merely planting an altered JPEG image, which
+ would have no obvious indications of what lurks inside. This action
+ prevents unwanted intrusion.
+ </para>
+
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para><screen>+inspect-jpegs</screen></para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="kill-popups">
+<title>kill-popups<anchor id="kill-popup"></title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Eliminate those annoying pop-up windows (deprecated)</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ While loading the document, replace JavaScript code that opens
+ pop-up windows with (syntactically neutral) dummy code on the fly.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Boolean.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ N/A
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ This action is basically a built-in, hardwired special-purpose filter
+ action, but there are important differences: For <literal>kill-popups</literal>,
+ the document need not be buffered, so it can be incrementally rendered while
+ downloading. But <literal>kill-popups</literal> doesn't catch as many pop-ups as
+ <literal><link
+ linkend="FILTER-ALL-POPUPS">filter{<replaceable>all-popups</replaceable>}</link></literal>
+ does and is not as smart as <literal><link
+ linkend="FILTER-UNSOLICITED-POPUPS">filter{<replaceable>unsolicited-popups</replaceable>}</link>
+ </literal>is.
+ </para>
+ <para>
+ 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 <literal><link linkend="filter">filter</link></literal> action,
+ since as soon as one <literal><link linkend="filter">filter</link></literal> applies,
+ the whole document needs to be buffered anyway, which destroys the advantage of
+ the <literal>kill-popups</literal> action over its filter equivalent.
+ </para>
+ <para>
+ Killing all pop-ups unconditionally is problematic. Many shops and banks rely on
+ pop-ups to display forms, shopping carts etc, and the <literal><link
+ linkend="FILTER-UNSOLICITED-POPUPS">filter{<replaceable>unsolicited-popups</replaceable>}</link>
+ </literal> does a fairly good job of catching only the unwanted ones.
+ </para>
+ <para>
+ If the only kind of pop-ups that you want to kill are exit consoles (those
+ <emphasis>really nasty</emphasis> windows that appear when you close an other
+ one), you might want to use
+ <literal><link
+ linkend="filter">filter</link>{<replaceable>js-annoyances</replaceable>}</literal>
+ instead.
+ </para>
+
+ <!--
+ <para>
+ An alternate spelling is <literal>+kill-popup</literal>, which is
+ interchangeable.
+ </para>
+ -->
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para><screen>+kill-popups</screen></para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="limit-connect">
+<title>limit-connect</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Prevent abuse of <application>Privoxy</application> as a TCP proxy relay or disable SSL for untrusted sites</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Specifies to which ports HTTP CONNECT requests are allowable.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ A comma-separated list of ports or port ranges (the latter using dashes, with the minimum
+ defaulting to 0 and the maximum to 65K).
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ By default, i.e. if no <literal>limit-connect</literal> action applies,
+ <application>Privoxy</application> only allows HTTP CONNECT
+ requests to port 443 (the standard, secure HTTPS port). Use
+ <literal>limit-connect</literal> if more fine-grained control is desired
+ for some or all destinations.
+ </para>
+ <para>
+ The CONNECT methods exists in HTTP to allow access to secure websites
+ (<quote>https://</quote> 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.
+ </para>
+ <para>
+ <application>Privoxy</application> relays HTTPS traffic without seeing
+ the decoded content. Websites can leverage this limitation to circumvent &my-app;'s
+ filters. By specifying an invalid port range you can disable HTTPS entirely.
+ If you plan to disable SSL by default, consider enabling
+ <literal><link linkend="treat-forbidden-connects-like-blocks ">treat-forbidden-connects-like-blocks</link></literal>
+ as well, to be able to quickly create exceptions.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usages:</term>
+ <listitem>
+ <!-- I had trouble getting the spacing to look right in my browser -->
+ <!-- I probably have the wrong font setup, bollocks. -->
+ <!-- Apparently the emphasis tag uses a proportional font no matter what -->
+ <para>
+ <screen>+limit-connect{443} # This is the default and need not be specified.
++limit-connect{80,443} # Ports 80 and 443 are OK.
++limit-connect{-3, 7, 20-100, 500-} # Ports less than 3, 7, 20 to 100 and above 500 are OK.
++limit-connect{-} # All ports are OK
++limit-connect{,} # No HTTPS/SSL traffic is allowed</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="prevent-compression">
+<title>prevent-compression</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>
+ Ensure that servers send the content uncompressed, so it can be
+ passed through <literal><link linkend="filter">filter</link></literal>s.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Removes the Accept-Encoding header which can be used to ask for compressed transfer.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Boolean.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ N/A
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ More and more websites send their content compressed by default, which
+ is generally a good idea and saves bandwidth. But for the <literal><link
+ linkend="filter">filter</link></literal>, <literal><link linkend="deanimate-gifs">deanimate-gifs</link></literal>
+ and <literal><link linkend="kill-popups">kill-popups</link></literal> actions to work,
+ <application>Privoxy</application> needs access to the uncompressed data.
+ Unfortunately, <application>Privoxy</application> 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.
+ </para>
+ <para>
+ This will slow down transfers from those websites, though. If you use any of the above-mentioned
+ actions, you will typically want to use <literal>prevent-compression</literal> in conjunction
+ with them.
+ </para>
+ <para>
+ Note that some (rare) ill-configured sites don't handle requests for uncompressed
+ documents correctly (they send an empty document body). If you use <literal>prevent-compression</literal>
+ per default, you'll have to add exceptions for those sites. See the example for how to do that.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage (sections):</term>
+ <listitem>
+ <para>
+ <screen># Set default:
+#
+{+prevent-compression}
+/ # Match all sites
+
+# Make exceptions for ill sites:
+#
+{-prevent-compression}
+www.debianhelp.org
+www.pclinuxonline.com</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="overwrite-last-modified">
+<title>overwrite-last-modified</title>
+<!--
+new action
+-->
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Prevent yet another way to track the user's steps between sessions.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Deletes the <quote>Last-Modified:</quote> HTTP server header or modifies its value.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ One of the keywords: <quote>block</quote>, <quote>reset-to-request-time</quote>
+ and <quote>randomize</quote>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ Removing the <quote>Last-Modified:</quote> header is useful for filter
+ testing, where you want to force a real reload instead of getting status
+ code <quote>304</quote>, which would cause the browser to reuse the old
+ version of the page.
+ </para>
+ <para>
+ The <quote>randomize</quote> option overwrites the value of the
+ <quote>Last-Modified:</quote> header with a randomly chosen time
+ between the original value and the current time. In theory the server
+ could send each document with a different <quote>Last-Modified:</quote>
+ header to track visits without using cookies. <quote>Randomize</quote>
+ makes it impossible and the browser can still revalidate cached documents.
+ </para>
+ <para>
+ <quote>reset-to-request-time</quote> overwrites the value of the
+ <quote>Last-Modified:</quote> header with the current time. You could use
+ this option together with
+ <literal><link linkend="hide-if-modified-since">hided-if-modified-since</link></literal>
+ to further customize your random range.
+ </para>
+ <para>
+ The preferred parameter here is <quote>randomize</quote>. It is safe
+ to use, as long as the time settings are more or less correct.
+ If the server sets the <quote>Last-Modified:</quote> header to the time
+ of the request, the random range becomes zero and the value stays the same.
+ Therefore you should later randomize it a second time with
+ <literal><link linkend="hide-if-modified-since">hided-if-modified-since</link></literal>,
+ just to be sure.
+ </para>
+ <para>
+ It is also recommended to use this action together with
+ <literal><link linkend="crunch-if-none-match">crunch-if-none-match</link></literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ <screen># Let the browser revalidate without being tracked across sessions
+{+hide-if-modified-since {-60}\
++overwrite-last-modified {randomize}\
++crunch-if-none-match}
+/</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="redirect">
+<title>redirect</title>
+<!--
+new action
+-->
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>
+ Redirect requests to other sites.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Convinces the browser that the requested document has been moved
+ to another location and the browser should get it from there.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ Any URL.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ This action is useful to replace whole documents with ones of your
+ choosing. This can be used to enforce safe surfing, or just as a simple
+ convenience.
+ </para>
+ <para>
+ You can do the same by combining the actions
+ <literal><link linkend="block">block</link></literal>,
+ <literal><link linkend="handle-as-image">handle-as-image</link></literal> and
+ <literal><link linkend="set-image-blocker">set-image-blocker{URL}</link></literal>.
+ It doesn't sound right for non-image documents, and that's why this action
+ was created.
+ </para>
+ <para>
+ This action will be ignored if you use it together with
+ <literal><link linkend="block">block</link></literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usages:</term>
+ <listitem>
+ <para>
+ <screen># Replace example.com's style sheet with another one
+{ +redirect{http://localhost/css-replacements/example.com.css} }
+ example.com/stylesheet.css
+
+# Create a short, easy to remember nickname for a favorite site
+{ +redirect{http://www.privoxy.org/user-manual/actions-file.html} }
+ a</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="send-vanilla-wafer">
+<title>send-vanilla-wafer</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>
+ Feed log analysis scripts with useless data.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Boolean.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ N/A
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ The vanilla wafer is a (relatively) unique header and could conceivably be used to track you.
+ </para>
+ <para>
+ This action is rarely used and not enabled in the default configuration.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ <screen>+send-vanilla-wafer</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="send-wafer">
+<title>send-wafer</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>
+ Send custom cookies or feed log analysis scripts with even more useless data.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Sends a custom, user-defined cookie with each request.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Multi-value.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ A string of the form <quote><replaceable class="option">name</replaceable>=<replaceable
+ class="parameter">value</replaceable></quote>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ Being multi-valued, multiple instances of this action can apply to the same request,
+ resulting in multiple cookies being sent.
+ </para>
+ <para>
+ This action is rarely used and not enabled in the default configuration.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>Example usage (section):</term>
+ <listitem>
+ <para>
+ <screen>{+send-wafer{UsingPrivoxy=true}}
+my-internal-testing-server.void</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="session-cookies-only">
+<title>session-cookies-only</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>
+ Allow only temporary <quote>session</quote> cookies (for the current
+ browser session <emphasis>only</emphasis>).
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ Deletes the <quote>expires</quote> field from <quote>Set-Cookie:</quote>
+ server headers. Most browsers will not store such cookies permanently and
+ forget them in between sessions.
+ </para>
+ </listitem>
+ </varlistentry>
+
+<varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Boolean.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>
+ N/A
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ This is less strict than <literal><link linkend="crunch-incoming-cookies">crunch-incoming-cookies</link></literal> /
+ <literal><link linkend="crunch-outgoing-cookies">crunch-outgoing-cookies</link></literal> and allows you to browse
+ websites that insist or rely on setting cookies, without compromising your privacy too badly.
+ </para>
+ <para>
+ Most browsers will not permanently store cookies that have been processed by
+ <literal>session-cookies-only</literal> 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.
+ </para>
+ <para>
+ It makes <emphasis>no sense at all</emphasis> to use <literal>session-cookies-only</literal>
+ together with <literal><link linkend="crunch-incoming-cookies">crunch-incoming-cookies</link></literal> or
+ <literal><link linkend="crunch-outgoing-cookies">crunch-outgoing-cookies</link></literal>. If you do, cookies
+ will be plainly killed.
+ </para>
+ <para>
+ Note that it is up to the browser how it handles such cookies without an <quote>expires</quote>
+ field. If you use an exotic browser, you might want to try it out to be sure.
+ </para>
+ <para>
+ This setting also has no effect on cookies that may have been stored
+ previously by the browser before starting <application>Privoxy</application>.
+ These would have to be removed manually.
+ </para>
+ <para>
+ <application>Privoxy</application> also uses
+ the <link linkend="filter-content-cookies">content-cookies filter</link>
+ to block some types of cookies. Content cookies are not effected by
+ <literal>session-cookies-only</literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ <screen>+session-cookies-only</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="set-image-blocker">
+<title>set-image-blocker</title>
+
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Choose the replacement for blocked images</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ This action alone doesn't do anything noticeable. If <emphasis>both</emphasis>
+ <literal><link linkend="block">block</link></literal> <emphasis>and</emphasis> <literal><link
+ linkend="handle-as-image">handle-as-image</link></literal> <emphasis>also</emphasis>
+ apply, i.e. if the request is to be blocked as an image,
+ <emphasis>then</emphasis> the parameter of this action decides what will be
+ sent as a replacement.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Parameterized.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <itemizedlist>
+ <listitem>
+ <para>
+ <quote>pattern</quote> to send a built-in checkerboard pattern image. The image is visually
+ decent, scales very well, and makes it obvious where banners were busted.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <quote>blank</quote> to send a built-in transparent image. This makes banners disappear
+ completely, but makes it hard to detect where <application>Privoxy</application> has blocked
+ images on a given page and complicates troubleshooting if <application>Privoxy</application>
+ has blocked innocent images, like navigation icons.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ <quote><replaceable class="parameter">target-url</replaceable></quote> to
+ send a redirect to <replaceable class="parameter">target-url</replaceable>. You can redirect
+ to any image anywhere, even in your local filesystem via <quote>file:///</quote> URL.
+ (But note that not all browsers support redirecting to a local file system).
+ </para>
+ <para>
+ A good application of redirects is to use special <application>Privoxy</application>-built-in
+ URLs, which send the built-in images, as <replaceable class="parameter">target-url</replaceable>.
+ This has the same visual effect as specifying <quote>blank</quote> or <quote>pattern</quote> in
+ the first place, but enables your browser to cache the replacement image, instead of requesting
+ it over and over again.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Notes:</term>
+ <listitem>
+ <para>
+ The URLs for the built-in images are <quote>http://config.privoxy.org/send-banner?type=<replaceable
+ class="parameter">type</replaceable></quote>, where <replaceable class="parameter">type</replaceable> is
+ either <quote>blank</quote> or <quote>pattern</quote>.
+ </para>
+ <para>
+ There is a third (advanced) type, called <quote>auto</quote>. It is <emphasis>NOT</emphasis> to be
+ used in <literal>set-image-blocker</literal>, but meant for use from <link linkend="filter-file">filters</link>.
+ Auto will select the type of image that would have applied to the referring page, had it been an image.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Example usage:</term>
+ <listitem>
+ <para>
+ Built-in pattern:
+ </para>
+ <para>
+ <screen>+set-image-blocker{pattern}</screen>
+ </para>
+ <para>
+ Redirect to the BSD devil:
+ </para>
+ <para>
+ <screen>+set-image-blocker{http://www.freebsd.org/gifs/dae_up3.gif}</screen>
+ </para>
+ <para>
+ Redirect to the built-in pattern for better caching:
+ </para>
+ <para>
+ <screen>+set-image-blocker{http://config.privoxy.org/send-banner?type=pattern}</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+</variablelist>
+</sect3>
+
+
+<!-- ~~~~~ New section ~~~~~ -->
+<sect3 renderas="sect4" id="treat-forbidden-connects-like-blocks">
+<title>treat-forbidden-connects-like-blocks</title>
+<!--
+new action
+-->
+<variablelist>
+ <varlistentry>
+ <term>Typical use:</term>
+ <listitem>
+ <para>Block forbidden connects with an easy to find error message.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Effect:</term>
+ <listitem>
+ <para>
+ If this action is enabled, <application>Privoxy</application> no longer
+ makes a difference between forbidden connects and ordinary blocks.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Type:</term>
+ <!-- Boolean, Parameterized, Multi-value -->
+ <listitem>
+ <para>Boolean</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>Parameter:</term>
+ <listitem>
+ <para>N/A</para>
+ </listitem>
+ </varlistentry>