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CLASS="SECT1"
><A
NAME="FILTER-FILE"
->9. The Filter File</A
+>9. Filter Files</A
></H1
><P
-> All text substitutions that can be invoked through the
+> On-the-fly text substitutions need
+ to be defined in a <SPAN
+CLASS="QUOTE"
+>"filter file"</SPAN
+>. Once defined, they
+ can then be invoked as an <SPAN
+CLASS="QUOTE"
+>"action"</SPAN
+>.</P
+><P
+> <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+> supports three different filter actions:
<TT
CLASS="LITERAL"
><A
HREF="actions-file.html#FILTER"
>filter</A
></TT
-> action
- must first be defined in the filter file, which is typically
- called <TT
-CLASS="FILENAME"
->default.filter</TT
-> and which can be
- selected through the <TT
+> to
+ rewrite the content that is send to the client,
+ <TT
+CLASS="LITERAL"
+><A
+HREF="actions-file.html#CLIENT-HEADER-FILTER"
+>client-header-filter</A
+></TT
+>
+ to rewrite headers that are send by the client, and
+ <TT
+CLASS="LITERAL"
+><A
+HREF="actions-file.html#SERVER-HEADER-FILTER"
+>server-header-filter</A
+></TT
+>
+ to rewrite headers that are send by the server.</P
+><P
+> <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+> also supports two tagger actions:
+ <TT
+CLASS="LITERAL"
+><A
+HREF="actions-file.html#CLIENT-HEADER-TAGGER"
+>client-header-tagger</A
+></TT
+>
+ and
+ <TT
+CLASS="LITERAL"
+><A
+HREF="actions-file.html#SERVER-HEADER-TAGGER"
+>server-header-tagger</A
+></TT
+>.
+ Taggers and filters use the same syntax in the filter files, the difference
+ is that taggers don't modify the text they are filtering, but use a rewritten
+ version of the filtered text as tag. The tags can then be used to change the
+ applying actions through sections with <A
+HREF="actions-file.html#TAG-PATTERN"
+>tag-patterns</A
+>.</P
+><P
+> Multiple filter files can be defined through the <TT
CLASS="LITERAL"
> <A
HREF="config.html#FILTERFILE"
>filterfile</A
></TT
-> config
- option.</P
+> config directive. The filters
+ as supplied by the developers are located in
+ <TT
+CLASS="FILENAME"
+>default.filter</TT
+>. It is recommended that any locally
+ defined or modified filters go in a separately defined file such as
+ <TT
+CLASS="FILENAME"
+>user.filter</TT
+>.
+ </P
><P
-> Typical reasons for doing such substitutions are to eliminate
- common annoyances in HTML and JavaScript, such as pop-up windows,
+> Common tasks for content filters 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.</P
+ or just to have fun.</P
><P
-> Filtering works on any text-based document type, including plain
- text, HTML, JavaScript, CSS etc. (all <TT
+> Enabled content filters are applied to any content whose
+ <SPAN
+CLASS="QUOTE"
+>"Content Type"</SPAN
+> header is recognised as a sign
+ of text-based content, with the exception of <TT
CLASS="LITERAL"
->text/*</TT
->
- MIME types). Substitutions are made at the source level, so if
- you want to <SPAN
+>text/plain</TT
+>.
+ Use the <A
+HREF="actions-file.html#FORCE-TEXT-MODE"
+>force-text-mode</A
+> action
+ to also filter other content.</P
+><P
+> Substitutions are made at the source level, so if you want to <SPAN
CLASS="QUOTE"
->"roll your own"</SPAN
-> filters, you should be
- familiar with HTML syntax.</P
+>"roll
+ your own"</SPAN
+> filters, you should first be familiar with HTML syntax,
+ and, of course, regular expressions.</P
><P
> Just like the <A
HREF="actions-file.html"
>actions files</A
>, the
- filter file is organized in sections, which are called <I
+ filter file is organized in sections, which are called <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>filters</I
+></SPAN
>
- here. Each filter consists of a heading line, that starts with the
- <I
+ here. Each filter consists of a heading line, that starts with one of the
+ <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
->keyword</I
+>keywords</I
+></SPAN
> <TT
CLASS="LITERAL"
>FILTER:</TT
->, followed by
- the filter's <I
+>,
+ <TT
+CLASS="LITERAL"
+>CLIENT-HEADER-FILTER:</TT
+> or <TT
+CLASS="LITERAL"
+>SERVER-HEADER-FILTER:</TT
+>
+ followed by the filter's <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>name</I
+></SPAN
>, and a short (one line)
- <I
+ <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>description</I
+></SPAN
> of what it does. Below that line
- come the <I
+ come the <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>jobs</I
+></SPAN
>, i.e. lines that define the actual
text substitutions. By convention, the name of a filter
- should describe what the filter <I
+ should describe what the filter <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>eliminates</I
+></SPAN
>. The
comment is used in the <A
HREF="http://config.privoxy.org/"
>actions file</A
>.</P
><P
-> A filter header line for a filter called <SPAN
+> Filter definitions start with a header line that contains the filter
+ type, the filter name and the filter description.
+ A content filter header line for a filter called <SPAN
CLASS="QUOTE"
>"foo"</SPAN
> could look
>s///</TT
> operator. If you are familiar with Perl, you
will find this to be quite intuitive, and may want to look at the
- <A
-HREF="http://www.oesterhelt.org/pcrs/pcrs.1.html"
-TARGET="_top"
->PCRS man page</A
->
- for the subtle differences to Perl behaviour. Most notably, the non-standard
- option letter <TT
+ PCRS documentation for the subtle differences to Perl behaviour. Most
+ notably, the non-standard option letter <TT
CLASS="LITERAL"
>U</TT
-> is supported, which turns the default
- to ungreedy matching.</P
+> is supported,
+ which turns the default to ungreedy matching.</P
><P
-> If you are new to regular expressions, you might want to take a look at
+> If you are new to
+ <A
+HREF="http://en.wikipedia.org/wiki/Regular_expressions"
+TARGET="_top"
+><SPAN
+CLASS="QUOTE"
+>"Regular
+ Expressions"</SPAN
+></A
+>, you might want to take a look at
the <A
HREF="appendix.html#REGEX"
>Appendix on regular expressions</A
>, and
see the <A
-HREF="http://perldoc.com/perl5.6.1/pod/perl.html"
+HREF="http://perldoc.perl.org/perlre.html"
TARGET="_top"
>Perl
manual</A
> for
<A
-HREF="http://perldoc.com/perl5.6.1/pod/perlop.html#s-PATTERN-REPLACEMENT-egimosx"
+HREF="http://perldoc.perl.org/perlop.html"
TARGET="_top"
>the
<TT
>s///</TT
> operator's syntax</A
> and <A
-HREF="http://perldoc.com/perl5.6.1/pod/perlre.html"
+HREF="http://perldoc.perl.org/perlre.html"
TARGET="_top"
>Perl-style regular
expressions</A
><H2
CLASS="SECT2"
><A
-NAME="AEN2902"
+NAME="AEN4439"
>9.1. Filter File Tutorial</A
></H2
><P
> Now, let's complete our <SPAN
CLASS="QUOTE"
>"foo"</SPAN
-> filter. We have already defined
+> content filter. We have already defined
the heading, but the jobs are still missing. Since all it does is to replace
<SPAN
CLASS="QUOTE"
></TABLE
></P
><P
-> But wait! Didn't the comment say that <I
+> But wait! Didn't the comment say that <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>all</I
+></SPAN
> occurrences
of <SPAN
CLASS="QUOTE"
matches <SPAN
CLASS="QUOTE"
>"<script"</SPAN
->, followed by <I
+>, followed by <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>any</I
+></SPAN
> text, i.e.
it matches the whole page, from the start of the first <script> tag.</P
><P
CLASS="QUOTE"
>"document.referrer"</SPAN
>. The dot needed to
- be <I
+ be <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>escaped</I
+></SPAN
>, 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 <SPAN
CLASS="QUOTE"
>"document.referrer"</SPAN
->, if <I
+>, if <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>both</I
+></SPAN
> are present
in the page (and appear in that order).</P
><P
text in between <SPAN
CLASS="QUOTE"
>"<script"</SPAN
-> and the <I
+> and the <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>first</I
+></SPAN
> occurrence
of <SPAN
CLASS="QUOTE"
CLASS="LITERAL"
>.*</TT
> will
- only span the text up to the <I
+ only span the text up to the <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>first</I
+></SPAN
> <SPAN
CLASS="QUOTE"
>"</script>"</SPAN
<TT
CLASS="LITERAL"
>"Not Your Business!"</TT
-> (<I
+> (<SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>including</I
+></SPAN
>
the quotation marks!), followed by the text remembered as <TT
CLASS="LITERAL"
CLASS="SCREEN"
># The status bar is for displaying link targets, not pointless blahblah
#
-s/window\.status\s*=\s*['"].*?['"]/dUmMy=1/ig</PRE
+s/window\.status\s*=\s*(['"]).*?\1/dUmMy=1/ig</PRE
></TD
></TR
></TABLE
> construct means: <SPAN
CLASS="QUOTE"
>"a single
- <I
+ <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>or</I
+></SPAN
> a double quote"</SPAN
->.</P
+>. Finally, <TT
+CLASS="LITERAL"
+>\1</TT
+> is
+ a back-reference to the first parenthesis just like <TT
+CLASS="LITERAL"
+>$1</TT
+> above,
+ with the difference that in the <SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>pattern</I
+></SPAN
+>, a backslash indicates
+ a back-reference, whereas in the <SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>substitute</I
+></SPAN
+>, it's the dollar.</P
><P
> So what does this job do? It replaces assignments of single- or double-quoted
strings to the <SPAN
CLASS="SCREEN"
># Kill OnUnload popups. Yummy. Test: http://www.zdnet.com/zdsubs/yahoo/tree/yfs.html
#
-s/(<body .*)onunload(.*>)/$1never$2/iU</PRE
+s/(<body [^>]*)onunload(.*>)/$1never$2/iU</PRE
></TD
></TR
></TABLE
TARGET="_top"
>OnUnload
event binding</A
-> in the HTML DOM was a <I
+> in the HTML DOM was a <SPAN
+CLASS="emphasis"
+><I
CLASS="EMPHASIS"
>CRIME</I
+></SPAN
>.
When I close a browser window, I want it to close and die. Basta.
This job replaces the <SPAN
CLASS="LITERAL"
>i</TT
> option makes the pattern matching
- case-insensitive.</P
+ case-insensitive. Also note that ungreedy matching alone doesn't always guarantee
+ a minimal match: In the first parenthesis, we had to use <TT
+CLASS="LITERAL"
+>[^>]*</TT
+>
+ instead of <TT
+CLASS="LITERAL"
+>.*</TT
+> to prevent the match from exceeding the
+ <body> tag if it doesn't contain <SPAN
+CLASS="QUOTE"
+>"OnUnload"</SPAN
+>, but the page's
+ content does.</P
><P
> The last example is from the fun department:</P
><P
CLASS="QUOTE"
>"microsoft"</SPAN
>
- in the page. This prevents links to microsoft.com from being messed, while
+ in the page. This prevents links to microsoft.com from being trashed, while
still replacing the word everywhere else.</P
><P
> <TABLE
#
s* industry[ -]leading \
| cutting[ -]edge \
+| customer[ -]focused \
+| market[ -]driven \
| award[ -]winning # Comments are OK, too! \
| high[ -]performance \
| solutions[ -]based \
CLASS="LITERAL"
>x</TT
> option in this job turns on extended syntax, and allows for
- e.g. the liberal use of (non-interpreted!) whitespace for nicer formatting.</P
+ e.g. the liberal use of (non-interpreted!) whitespace for nicer formatting. </P
><P
> You get the idea?</P
></DIV
+><DIV
+CLASS="SECT2"
+><H2
+CLASS="SECT2"
+><A
+NAME="PREDEFINED-FILTERS"
+>9.2. The Pre-defined Filters</A
+></H2
+><P
+>The distribution <TT
+CLASS="FILENAME"
+>default.filter</TT
+> file contains a selection of
+pre-defined filters for your convenience:</P
+><P
+></P
+><DIV
+CLASS="VARIABLELIST"
+><DL
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>js-annoyances</I
+></SPAN
+></DT
+><DD
+><P
+> The purpose of this filter is to get rid of particularly annoying JavaScript abuse.
+ To that end, it
+ <P
+></P
+><UL
+><LI
+><P
+> replaces JavaScript references to the browser's referrer information
+ with the string "Not Your Business!". This compliments the <TT
+CLASS="LITERAL"
+><A
+HREF="actions-file.html#HIDE-REFERRER"
+>hide-referrer</A
+></TT
+> action on the content level.
+ </P
+></LI
+><LI
+><P
+> removes the bindings to the DOM's
+ <A
+HREF="http://www.w3.org/TR/2000/REC-DOM-Level-2-Events-20001113/events.html#Events-eventgroupings-htmlevents"
+TARGET="_top"
+>unload
+ event</A
+> which we feel has no right to exist and is responsible for most <SPAN
+CLASS="QUOTE"
+>"exit consoles"</SPAN
+>, i.e.
+ nasty windows that pop up when you close another one.
+ </P
+></LI
+><LI
+><P
+> removes code that causes new windows to be opened with undesired properties, such as being
+ full-screen, non-resizeable, without location, status or menu bar etc.
+ </P
+></LI
+></UL
+>
+ </P
+><P
+> Use with caution. This is an aggressive filter, and can break sites that
+ rely heavily on JavaScript.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>js-events</I
+></SPAN
+></DT
+><DD
+><P
+> 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. Use with caution!
+ </P
+><P
+> We <SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>strongly discourage</I
+></SPAN
+> 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).
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>html-annoyances</I
+></SPAN
+></DT
+><DD
+><P
+> This filter will undo many common instances of HTML based abuse.
+ </P
+><P
+> The <TT
+CLASS="LITERAL"
+>BLINK</TT
+> and <TT
+CLASS="LITERAL"
+>MARQUEE</TT
+> tags
+ are neutralized (yeah baby!), and browser windows will be created as
+ resizeable (as of course they should be!), and will have location,
+ scroll and menu bars -- even if specified otherwise.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>content-cookies</I
+></SPAN
+></DT
+><DD
+><P
+> Most cookies are set in the HTTP dialog, where they can be intercepted
+ by the
+ <TT
+CLASS="LITERAL"
+><A
+HREF="actions-file.html#CRUNCH-INCOMING-COOKIES"
+>crunch-incoming-cookies</A
+></TT
+>
+ and <TT
+CLASS="LITERAL"
+><A
+HREF="actions-file.html#CRUNCH-OUTGOING-COOKIES"
+>crunch-outgoing-cookies</A
+></TT
+>
+ actions. But web sites increasingly make use of HTML meta tags and JavaScript
+ to sneak cookies to the browser on the content level.
+ </P
+><P
+> This filter disables most HTML and JavaScript code that reads or sets
+ cookies. It cannot detect all clever uses of these types of code, so it
+ should not be relied on as an absolute fix. Use it wherever you would also
+ use the cookie crunch actions.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>refresh tags</I
+></SPAN
+></DT
+><DD
+><P
+> 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.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>unsolicited-popups</I
+></SPAN
+></DT
+><DD
+><P
+> This filter attempts to prevent only <SPAN
+CLASS="QUOTE"
+>"unsolicited"</SPAN
+> 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.
+ </P
+><P
+> Technical note: The filter works by redefining the window.open JavaScript
+ function to a dummy function, <TT
+CLASS="LITERAL"
+>PrivoxyWindowOpen()</TT
+>,
+ during the loading and rendering phase of each HTML page access, and
+ restoring the function afterward.
+ </P
+><P
+> This is recommended only for browsers that cannot perform this function
+ reliably themselves. And be aware that some sites require such windows
+ in order to function normally. Use with caution.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>all-popups</I
+></SPAN
+></DT
+><DD
+><P
+> Attempt to prevent <SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>all</I
+></SPAN
+> pop-up windows from opening.
+ Note this should be used with even more discretion than the above, since
+ it is more likely to break some sites that require pop-ups for normal
+ usage. Use with caution.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>img-reorder</I
+></SPAN
+></DT
+><DD
+><P
+> This is a helper filter that has no value if used alone. It makes the
+ <TT
+CLASS="LITERAL"
+>banners-by-size</TT
+> and <TT
+CLASS="LITERAL"
+>banners-by-link</TT
+>
+ (see below) filters more effective and should be enabled together with them.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>banners-by-size</I
+></SPAN
+></DT
+><DD
+><P
+> 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.
+ </P
+><P
+> 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.
+ </P
+><P
+> Recommended only for those who require extreme ad blocking. The default
+ block rules should catch 95+% of all ads <SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>without</I
+></SPAN
+> this filter enabled.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>banners-by-link</I
+></SPAN
+></DT
+><DD
+><P
+> 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.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>webbugs</I
+></SPAN
+></DT
+><DD
+><P
+> 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 user ever becoming aware of the interaction with the third-party site.
+ HTML-ized spam also uses a similar technique to verify email addresses.
+ </P
+><P
+> This filter removes the HTML code that loads such <SPAN
+CLASS="QUOTE"
+>"webbugs"</SPAN
+>.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>tiny-textforms</I
+></SPAN
+></DT
+><DD
+><P
+> 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.
+ </P
+><P
+> It is not recommended to use this filter as a default.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>jumping-windows</I
+></SPAN
+></DT
+><DD
+><P
+> 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. Use with caution.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>frameset-borders</I
+></SPAN
+></DT
+><DD
+><P
+> 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.
+ </P
+><P
+> This filter removes the related HTML code. It should only be applied to sites
+ which need it.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>demoronizer</I
+></SPAN
+></DT
+><DD
+><P
+> Many Microsoft products that generate HTML use non-standard extensions (read:
+ violations) of the ISO 8859-1 aka Latin-1 character set. This can cause those
+ HTML documents to display with errors on standard-compliant platforms.
+ </P
+><P
+> 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 weird garbage characters
+ sometimes appear on some pages, or user agents that don't correct for this on
+ the fly.
+
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>shockwave-flash</I
+></SPAN
+></DT
+><DD
+><P
+> 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.
+ </P
+><P
+> </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>quicktime-kioskmode</I
+></SPAN
+></DT
+><DD
+><P
+> Change HTML code that embeds Quicktime objects so that kioskmode, which
+ prevents saving, is disabled.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>fun</I
+></SPAN
+></DT
+><DD
+><P
+> Text replacements for subversive browsing fun. Make fun of your favorite
+ Monopolist or play buzzword bingo.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>crude-parental</I
+></SPAN
+></DT
+><DD
+><P
+> A demonstration-only filter that shows how <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+>
+ can be used to delete web content on a keyword basis.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>ie-exploits</I
+></SPAN
+></DT
+><DD
+><P
+> An experimental collection of text replacements to disable malicious HTML and JavaScript
+ code that exploits known security holes in Internet Explorer.
+ </P
+><P
+> Presently, it only protects against Nimda and a cross-site scripting bug, and
+ would need active maintenance to provide more substantial protection.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>site-specifics</I
+></SPAN
+></DT
+><DD
+><P
+> Some web sites have very specific problems, the cure for which doesn't apply
+ anywhere else, or could even cause damage on other sites.
+ </P
+><P
+> 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
+ <TT
+CLASS="FILENAME"
+>default.action</TT
+> file does. Users shouldn't need to change
+ anything regarding this filter.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>google</I
+></SPAN
+></DT
+><DD
+><P
+> A CSS based block for Google text ads. Also removes a width limitation
+ and the toolbar advertisement.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>yahoo</I
+></SPAN
+></DT
+><DD
+><P
+> Another CSS based block, this time for Yahoo text ads. And removes
+ a width limitation as well.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>msn</I
+></SPAN
+></DT
+><DD
+><P
+> Another CSS based block, this time for MSN text ads. And removes
+ tracking URLs, as well as a width limitation.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>blogspot</I
+></SPAN
+></DT
+><DD
+><P
+> Cleans up some Blogspot blogs. Read the fine print before using this one!
+ </P
+><P
+> This filter also intentionally removes some navigation stuff and sets the
+ page width to 100%. As a result, some rounded <SPAN
+CLASS="QUOTE"
+>"corners"</SPAN
+> would
+ appear to early or not at all and as fixing this would require a browser
+ that understands background-size (CSS3), they are removed instead.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>xml-to-html</I
+></SPAN
+></DT
+><DD
+><P
+> Server-header filter to change the Content-Type from xml to html.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>html-to-xml</I
+></SPAN
+></DT
+><DD
+><P
+> Server-header filter to change the Content-Type from html to xml.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>no-ping</I
+></SPAN
+></DT
+><DD
+><P
+> Removes the non-standard <TT
+CLASS="LITERAL"
+>ping</TT
+> attribute from
+ anchor and area HTML tags.
+ </P
+></DD
+><DT
+><SPAN
+CLASS="emphasis"
+><I
+CLASS="EMPHASIS"
+>hide-tor-exit-notation</I
+></SPAN
+></DT
+><DD
+><P
+> Client-header filter to remove the <B
+CLASS="COMMAND"
+>Tor</B
+> exit node notation
+ found in Host and Referer headers.
+ </P
+><P
+> If <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+> and <B
+CLASS="COMMAND"
+>Tor</B
+> are chained and <SPAN
+CLASS="APPLICATION"
+>Privoxy</SPAN
+>
+ is configured to use socks4a, one can use <SPAN
+CLASS="QUOTE"
+>"http://www.example.org.foobar.exit/"</SPAN
+>
+ to access the host <SPAN
+CLASS="QUOTE"
+>"www.example.org"</SPAN
+> through the
+ <B
+CLASS="COMMAND"
+>Tor</B
+> exit node <SPAN
+CLASS="QUOTE"
+>"foobar"</SPAN
+>.
+ </P
+><P
+> As the HTTP client isn't aware of this notation, it treats the
+ whole string <SPAN
+CLASS="QUOTE"
+>"www.example.org.foobar.exit"</SPAN
+> as host and uses it
+ for the <SPAN
+CLASS="QUOTE"
+>"Host"</SPAN
+> and <SPAN
+CLASS="QUOTE"
+>"Referer"</SPAN
+> headers. From the
+ server's point of view the resulting headers are invalid and can cause problems.
+ </P
+><P
+> An invalid <SPAN
+CLASS="QUOTE"
+>"Referer"</SPAN
+> header can trigger <SPAN
+CLASS="QUOTE"
+>"hot-linking"</SPAN
+>
+ protections, an invalid <SPAN
+CLASS="QUOTE"
+>"Host"</SPAN
+> header will make it impossible for
+ the server to find the right vhost (several domains hosted on the same IP address).
+ </P
+><P
+> This client-header filter removes the <SPAN
+CLASS="QUOTE"
+>"foo.exit"</SPAN
+> part in those headers
+ to prevent the mentioned problems. Note that it only modifies
+ the HTTP headers, it doesn't make it impossible for the server
+ to detect your <B
+CLASS="COMMAND"
+>Tor</B
+> exit node based on the IP address
+ the request is coming from.
+ </P
+></DD
+></DL
+></DIV
+></DIV
></DIV
><DIV
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><HR
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WIDTH="100%"><TABLE
+SUMMARY="Footer navigation table"
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+ACCESSKEY="P"
>Prev</A
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+ACCESSKEY="H"
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+ACCESSKEY="N"
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