+</sect2>
+
+<!-- ~~~~~~~~ New section Header ~~~~~~~~~ -->
+
+<sect2 id="predefined-filters"><title>The Pre-defined Filters</title>
+
+<!--
+
+ Note each filter is also listed in the +filter action section above. Please
+ keep these listings in sync.
+
+-->
+
+<para>
+The distribution <filename>default.filter</filename> file contains a selection of
+pre-defined filters for your convenience:
+</para>
+
+<variablelist>
+ <varlistentry>
+ <term><emphasis>js-annoyances</emphasis></term>
+ <listitem>
+ <para>
+ The purpose of this filter is to get rid of particularly annoying JavaScript abuse.
+ To that end, it
+ <itemizedlist>
+ <listitem>
+ <para>
+ replaces JavaScript references to the browser's referrer information
+ with the string "Not Your Business!". This compliments the <literal><link
+ linkend="hide-referrer">hide-referrer</link></literal> action on the content level.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ removes the bindings to the DOM's
+ <ulink url="http://www.w3.org/TR/2000/REC-DOM-Level-2-Events-20001113/events.html#Events-eventgroupings-htmlevents">unload
+ event</ulink> which we feel has no right to exist and is responsible for most <quote>exit consoles</quote>, i.e.
+ nasty windows that pop up when you close another one.
+ </para>
+ </listitem>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </itemizedlist>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>js-events</emphasis></term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ <para>
+ We <emphasis>strongly discourage</emphasis> 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).
+ </para>
+ </listitem>
+ </varlistentry>
+
+<varlistentry>
+ <term><emphasis>html-annoyances</emphasis></term>
+ <listitem>
+ <para>
+ This filter will undo many common instances of HTML based abuse.
+ </para>
+ <para>
+ The <literal>BLINK</literal> and <literal>MARQUEE</literal> 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>content-cookies</emphasis></term>
+ <listitem>
+ <para>
+ Most cookies are set in the HTTP dialogue, where they can be intercepted
+ by the
+ <literal><link linkend="crunch-incoming-cookies">crunch-incoming-cookies</link></literal>
+ and <literal><link linkend="crunch-outgoing-cookies">crunch-outgoing-cookies</link></literal>
+ actions. But web sites increasingly make use of HTML meta tags and JavaScript
+ to sneak cookies to the browser on the content level.
+ </para>
+ <para>
+ This filter disables HTML and JavaScript code that reads or sets cookies. Use
+ it wherever you would also use the cookie crunch actions.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>refresh tags</emphasis></term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>unsolicited-popups</emphasis></term>
+ <listitem>
+ <para>
+ This filter attempts to prevent only <quote>unsolicited</quote> 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.
+ </para>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>all-popups</emphasis></term>
+ <listitem>
+ <para>
+ Attempt to prevent <emphasis>all</emphasis> 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>img-reorder</emphasis></term>
+ <listitem>
+ <para>
+ This is a helper filter that has no value if used alone. It makes the
+ <literal>banners-by-size</literal> and <literal>banners-by-link</literal>
+ (see below) filters more effective and should be enabled together with them.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>banners-by-size</emphasis></term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>banners-by-link</emphasis></term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>webbugs</emphasis></term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ <para>
+ This filter removes the HTML code that loads such <quote>webbugs</quote>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>tiny-textforms</emphasis></term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ <para>
+ It is not recommended to use this filter as a default.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>jumping-windows</emphasis></term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>frameset-borders</emphasis></term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ <para>
+ This filter removes the related HTML code. It should only be applied to sites
+ which need it.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>demoronizer</emphasis></term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>shockwave-flash</emphasis></term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ <para>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>quicktime-kioskmode</emphasis></term>
+ <listitem>
+ <para>
+ Change HTML code that embeds Quicktime objects so that kioskmode, which
+ prevents saving, is disabled.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>fun</emphasis></term>
+ <listitem>
+ <para>
+ Text replacements for subversive browsing fun. Make fun of your favorite
+ Monopolist or play buzzword bingo.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>crude-parental</emphasis></term>
+ <listitem>
+ <para>
+ A demonstration-only filter that shows how <application>Privoxy</application>
+ can be used to delete web content on a keyword basis.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>ie-exploits</emphasis></term>
+ <listitem>
+ <para>
+ A collection of text replacements to disable malicious HTML and JavaScript
+ code that exploits known security holes in Internet Explorer.
+ </para>
+ <para>
+ Presently, it only protects against Nimda and a cross-site scripting bug, and
+ would need active maintenance to provide more substantial protection.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><emphasis>site-specifics</emphasis></term>
+ <listitem>
+ <para>
+ Some web sites have very specific problems, the cure for which doesn't apply
+ anywhere else, or could even cause damage on other sites.
+ </para>
+ <para>
+ 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
+ <filename>default.action</filename> file does. Users shouldn't need to change
+ anything regarding this filter.
+ </para>
+ </listitem>
+ </varlistentry>
+
+<!--
+ <varlistentry>
+ <term><emphasis> </emphasis></term>
+ <listitem>
+ <para>
+ </para>
+ <para>
+ </para>
+ </listitem>
+ </varlistentry>
+-->
+</variablelist>
+