-# forward 127.*.*.*/ .
- </PRE
-></TD
-></TR
-></TABLE
-></P
-><P
-> Unencrypted connections to systems in these address ranges will
- be as (un)secure as the local network is, but the alternative is
- that your browser can't reach the network at all. Then again,
- that may actually be desired and if you don't know for sure
- that your browser has to be able to reach the local network,
- there's no reason to allow it.</P
-><P
-> If you want your browser to be able to reach servers in your local
- network by using their names, you will need additional exceptions
- that look like this:</P
-><P
-> <TABLE
-BORDER="0"
-BGCOLOR="#E0E0E0"
-WIDTH="100%"
-><TR
-><TD
-><PRE
-CLASS="SCREEN"
-># forward localhost/ .
- </PRE
-></TD
-></TR
-></TABLE
-></P
-><P
-> Save the modified configuration file and open
- <A
-HREF="http://config.privoxy.org/show-status"
-TARGET="_top"
->http://config.privoxy.org/show-status/</A
->
- in your browser, confirm that <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> has reloaded its configuration
- and that there are no other forward lines, unless you know that you need them. If everything looks good,
- refer to
- <A
-HREF="https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#IsMyConnectionPrivate"
-TARGET="_top"
->Tor
- Faq 4.2</A
-> to learn how to verify that you are really using <SPAN
-CLASS="APPLICATION"
->Tor</SPAN
->.</P
-><P
-> Afterward, please take the time to at least skim through the rest
- of <SPAN
-CLASS="APPLICATION"
->Tor's</SPAN
-> documentation. Make sure you understand
- what <SPAN
-CLASS="APPLICATION"
->Tor</SPAN
-> does, why it is no replacement for
- application level security, and why you probably don't want to
- use it for unencrypted logins.</P
-></DIV
-><DIV
-CLASS="SECT2"
-><H3
-CLASS="SECT2"
-><A
-NAME="AEN868"
->4.11. Might some things break because header information or
-content is being altered?</A
-></H3
-><P
-> Definitely. It is common for sites to use browser type, browser version,
- HTTP header content, and various other techniques in order to dynamically
- decide what to display and how to display it. What you see, and what I see,
- might be very different. There are many, many ways that this can be handled,
- so having hard and fast rules, is tricky.</P
-><P
-> The <SPAN
-CLASS="QUOTE"
->"User-Agent"</SPAN
-> is sometimes used in this way to identify
- the browser, and adjust content accordingly.</P
-><P
-> Also, different browsers use different encodings of non-English
- characters, certain web servers convert pages on-the-fly according to the
- User Agent header. Giving a <SPAN
-CLASS="QUOTE"
->"User Agent"</SPAN
-> with the wrong
- operating system or browser manufacturer causes some sites in these languages
- to be garbled; Surfers to Eastern European sites should change it to
- something closer. And then some page access counters work by looking at the
- <SPAN
-CLASS="QUOTE"
->"Referer"</SPAN
-> header; they may fail or break if unavailable. The
- weather maps of Intellicast have been blocked by their server when no
- <SPAN
-CLASS="QUOTE"
->"Referer"</SPAN
-> or cookie is provided, is another example. (But you
- can forge both headers without giving information away). There are
- many other ways things can go wrong when trying to fool a web server. The
- results of which could inadvertently cause pages to load incorrectly,
- partially, or even not at all. And there may be no obvious clues as to just
- what went wrong, or why. Nowhere will there be a message that says
- <SPAN
-CLASS="QUOTE"
->"<SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->Turn off <TT
-CLASS="LITERAL"
->fast-redirects</TT
-> or else!</I
-></SPAN
->
- "</SPAN
-></P
-><P
-> Similar thoughts apply to modifying JavaScript, and, to a lesser degree,
- HTML elements.</P
-><P
-> If you have problems with a site, you will have to adjust your configuration
- accordingly. Cookies are probably the most likely adjustment that may
- be required, but by no means the only one.</P
-></DIV
-><DIV
-CLASS="SECT2"
-><H3
-CLASS="SECT2"
-><A
-NAME="AEN882"
->4.12. Can Privoxy act as a <SPAN
-CLASS="QUOTE"
->"caching"</SPAN
-> proxy to
-speed up web browsing?</A
-></H3
-><P
-> No, it does not have this ability at all. You want something like
- <A
-HREF="http://www.squid-cache.org/"
-TARGET="_top"
->Squid</A
-> or
- <A
-HREF="http://www.pps.jussieu.fr/~jch/software/polipo/"
-TARGET="_top"
->Polipo</A
-> for this.
- And, yes, before you ask, <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> can co-exist
- with other kinds of proxies like <SPAN
-CLASS="APPLICATION"
->Squid</SPAN
->.
- See the <A
-HREF="../user-manual/config.html#FORWARDING"
-TARGET="_top"
->forwarding
- chapter</A
-> in the <A
-HREF="../user-manual/index.html"
-TARGET="_top"
->user
- manual</A
-> for details.</P
-></DIV
-><DIV
-CLASS="SECT2"
-><H3
-CLASS="SECT2"
-><A
-NAME="AEN892"
->4.13. What about as a firewall? Can Privoxy protect me?</A
-></H3
-><P
-> Not in the way you mean, or in the way some firewall vendors claim they can.
- <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> can help protect your privacy, but can't
- protect your system from intrusion attempts. It is, of course, perfectly possible
- to use <SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->both</I
-></SPAN
->.</P
-></DIV
-><DIV
-CLASS="SECT2"
-><H3
-CLASS="SECT2"
-><A
-NAME="AEN897"
->4.14. I have large empty spaces / a checkerboard pattern now where
-ads used to be. Why?</A
-></H3
-><P
-> It is technically possible to eliminate banners and ads in a way that frees
- their allocated page space. This could easily be done by blocking with
- <SPAN
-CLASS="APPLICATION"
->Privoxy's</SPAN
-> filters,
- and eliminating the <SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->entire</I
-></SPAN
-> image references from the
- HTML page source. </P
-><P
-> But, this would consume considerably more CPU resources (IOW, slow things
- down), would likely destroy the layout of some web pages which rely on the
- banners utilizing a certain amount of page space, and might fail in other
- cases, where the screen space is reserved (e.g. by HTML tables for instance).
- Also, making ads and banners disappear without any trace complicates
- troubleshooting, and would sooner or later be problematic.</P
-><P
-> The better alternative is to instead let them stay, and block the resulting
- requests for the banners themselves as is now the case. This leaves either
- empty space, or the familiar checkerboard pattern.</P
-><P
-> So the developers won't support this in the default configuration, but you
- can of course define appropriate filters yourself to achieve this.</P
-></DIV
-><DIV
-CLASS="SECT2"
-><H3
-CLASS="SECT2"
-><A
-NAME="AEN905"
->4.15. How can Privoxy filter Secure (HTTPS) URLs?</A
-></H3
-><P
-> Since secure HTTP connections are encrypted SSL sessions between your browser
- and the secure site, and are meant to be reliably <SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->secure</I
-></SPAN
->,
- there is little that <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> can do but hand the raw
- gibberish data though from one end to the other unprocessed.</P
-><P
-> The only exception to this is blocking by host patterns, as the client needs
- to tell <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> the name of the remote server,
- so that <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> can establish the connection.
- If that name matches a host-only pattern, the connection will be blocked.</P
-><P
-> As far as ad blocking is concerned, this is less of a restriction than it may
- seem, since ad sources are often identifiable by the host name, and often
- the banners to be placed in an encrypted page come unencrypted nonetheless
- for efficiency reasons, which exposes them to the full power of
- <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
->'s ad blocking.</P
-><P
-> <SPAN
-CLASS="QUOTE"
->"Content cookies"</SPAN
-> (those that are embedded in the actual HTML or
- JS page content, see <TT
-CLASS="LITERAL"
-><A
-HREF="../user-manual/actions-file.html#FILTER-CONTENT-COOKIES"
-TARGET="_top"
->filter{content-cookies}</A
-></TT
->),
- in an SSL transaction will be impossible to block under these conditions.
- Fortunately, this does not seem to be a very common scenario since most
- cookies come by traditional means.</P
-></DIV
-><DIV
-CLASS="SECT2"
-><H3
-CLASS="SECT2"
-><A
-NAME="AEN919"
->4.16. Privoxy runs as a <SPAN
-CLASS="QUOTE"
->"server"</SPAN
->. How
-secure is it? Do I need to take any special precautions?</A
-></H3
-><P
-> On Unix-like systems, <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> can run as a non-privileged
- user, which is how we recommend it be run. Also, by default
- <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> listens to requests from <SPAN
-CLASS="QUOTE"
->"localhost"</SPAN
->
- only.</P
-><P
-> The server aspect of <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> is not itself directly
- exposed to the Internet in this configuration. If you want to have
- <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> serve as a LAN proxy, this will have to
- be opened up to allow for LAN requests. In this case, we'd recommend
- you specify only the LAN gateway address, e.g. 192.168.1.1, in the main
- <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> configuration file and check all <A
-HREF="../user-manual/config.html#ACCESS-CONTROL"
-TARGET="_top"
->access control and security
- options</A
->. All LAN hosts can then use this as their proxy address
- in the browser proxy configuration, but <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
->
- will not listen on any external interfaces. ACLs can be defined in addition,
- and using a firewall is always good too. Better safe than sorry.</P
-></DIV
-><DIV
-CLASS="SECT2"
-><H3
-CLASS="SECT2"
-><A
-NAME="TURNOFF"
->4.17. Can I temporarily disable Privoxy?</A
-></H3
-><P
-> <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> doesn't have a transparent proxy mode,
- but you can toggle off blocking and content filtering.</P
-><P
-> The easiest way to do that is to point your browser
- to the remote toggle URL: <A
-HREF="http://config.privoxy.org/toggle"
-TARGET="_top"
->http://config.privoxy.org/toggle</A
->.</P
-><P
-> See the <A
-HREF="../user-manual/appendix.html#BOOKMARKLETS"
-TARGET="_top"
->Bookmarklets section</A
->
- of the <I
-CLASS="CITETITLE"
->User Manual</I
-> for an easy way to access this
- feature. Note that this is a feature that may need to be enabled in the main
- <TT
-CLASS="FILENAME"
->config</TT
-> file.</P
-></DIV
-><DIV
-CLASS="SECT2"
-><H3
-CLASS="SECT2"
-><A
-NAME="REALLYOFF"
->4.18. When <SPAN
-CLASS="QUOTE"
->"disabled"</SPAN
-> is Privoxy totally
-out of the picture?</A
-></H3
-><P
-> No, this just means all optional filtering and actions are disabled.
- <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> is still acting as a proxy, but just
- doing less of the things that <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> would
- normally be expected to do. It is still a <SPAN
-CLASS="QUOTE"
->"middle-man"</SPAN
-> in
- the interaction between your browser and web sites. See below to bypass
- the proxy.</P
-></DIV
-><DIV
-CLASS="SECT2"
-><H3
-CLASS="SECT2"
-><A
-NAME="TURNOFF2"
->4.19. How can I tell Privoxy to totally ignore certain sites?</A
-></H3
-><P
-> Bypassing a proxy, or proxying based on arbitrary criteria, is purely a browser
- configuration issue, not a <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> issue. Modern browsers typically do have
- settings for not proxying certain sites. Check your browser's help files.</P
-></DIV
-><DIV
-CLASS="SECT2"
-><H3
-CLASS="SECT2"
-><A
-NAME="CRUNCH"
->4.20. My logs show Privoxy <SPAN
-CLASS="QUOTE"
->"crunches"</SPAN
->
-ads, but also its own internal CGI pages. What is a <SPAN
-CLASS="QUOTE"
->"crunch"</SPAN
->?</A
-></H3
-><P
-> A <SPAN
-CLASS="QUOTE"
->"crunch"</SPAN
-> simply means <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> intercepted
- <SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->something</I
-></SPAN
->, nothing more. Often this is indeed ads or
- banners, but <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> uses the same mechanism for
- trapping requests for its own internal pages. For instance, a request for
- <SPAN
-CLASS="APPLICATION"
->Privoxy's</SPAN
-> configuration page at: <A
-HREF="http://config.privoxy.org"
-TARGET="_top"
->http://config.privoxy.org</A
->, is
- intercepted (i.e. it does not go out to the 'net), and the familiar CGI
- configuration is returned to the browser, and the log consequently will show
- a <SPAN
-CLASS="QUOTE"
->"crunch"</SPAN
->.</P
-><P
-> Since version 3.0.7, Privoxy will also log the crunch reason.
- If you are using an older version you might want to upgrade.</P
-></DIV
-><DIV
-CLASS="SECT2"
-><H3
-CLASS="SECT2"
-><A
-NAME="DOWNLOADS"
->4.21. Can Privoxy effect files that I download
-from a webserver? FTP server?</A
-></H3
-><P
-> From the webserver's perspective, there is no difference between
- viewing a document (i.e. a page), and downloading a file. The same is true of
- <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
->. If there is a match for a <TT
-CLASS="LITERAL"
-><A
-HREF="../user-manual/actions-file.html#BLOCK"
-TARGET="_top"
->block</A
-></TT
-> pattern,
- it will still be blocked, and of course this is obvious.
- </P
-><P
-> Filtering is potentially more of a concern since the results are not always
- so obvious, and the effects of filtering are there whether the file is simply
- viewed, or downloaded. And potentially whether the content is some obnoxious
- advertisement, or Mr. Jimmy's latest/greatest source code jewel. Of course,
- one of these presumably is <SPAN
-CLASS="QUOTE"
->"bad"</SPAN
-> content that we don't want, and
- the other is <SPAN
-CLASS="QUOTE"
->"good"</SPAN
-> content that we do want.
- <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> is blind to the differences, and can only
- distinguish <SPAN
-CLASS="QUOTE"
->"good from bad"</SPAN
-> by the configuration parameters
- <SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->we</I
-></SPAN
-> give it.</P
-><P
-> <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> knows the differences in files according
- to the <SPAN
-CLASS="QUOTE"
->"Content Type"</SPAN
-> as reported by the webserver. If this is
- reported accurately (e.g. <SPAN
-CLASS="QUOTE"
->"application/zip"</SPAN
-> for a zip archive),
- then <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> knows to ignore these where
- appropriate. <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> potentially can filter HTML
- as well as plain text documents, subject to configuration parameters of
- course. Also, documents that are of an unknown type (generally assumed to be
- <SPAN
-CLASS="QUOTE"
->"text/plain"</SPAN
->) can be filtered, as will those that might be
- incorrectly reported by the webserver. If such a file is a downloaded file
- that is intended to be saved to disk, then any content that might have been
- altered by filtering, will be saved too, for these (probably rare) cases.</P
-><P
-> Note that versions later than 3.0.2 do NOT filter document types reported as
- <SPAN
-CLASS="QUOTE"
->"text/plain"</SPAN
->. Prior to this, <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
->
- did filter this document type.</P
-><P
-> In short, filtering is <SPAN
-CLASS="QUOTE"
->"ON"</SPAN
-> if a) the content type as reported
- by the webserver is appropriate <SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->and</I
-></SPAN
-> b) the configuration
- allows it (or at least does not disallow it). That's it. There is no magic
- cookie anywhere to say this is <SPAN
-CLASS="QUOTE"
->"good"</SPAN
-> and this is
- <SPAN
-CLASS="QUOTE"
->"bad"</SPAN
->. It's the configuration that lets it all happen or not.</P
-><P
-> If you download text files, you probably do not want these to be filtered,
- particularly if the content is source code, or other critical content. Source
- code sometimes might be mistaken for Javascript (i.e. the kind that might
- open a pop-up window). It is recommended to turn off filtering for download
- sites (particularly if the content may be plain text files and you are using
- version 3.0.2 or earlier) in your <TT
-CLASS="FILENAME"
->user.action</TT
-> file. And
- also, for any site or page where making <SPAN
-CLASS="emphasis"
-><I
-CLASS="EMPHASIS"
->any</I
-></SPAN
-> changes at
- all to the content is to be avoided.</P
-><P
-> <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
-> does not do FTP at all, only HTTP
- and HTTPS (SSL) protocols.</P
-></DIV
-><DIV
-CLASS="SECT2"
-><H3
-CLASS="SECT2"
-><A
-NAME="DOWNLOADS2"
->4.22. I just downloaded a Perl script, and Privoxy
-altered it! Yikes, what is wrong!</A
-></H3
-><P
-> Please read above.</P
-></DIV
-><DIV
-CLASS="SECT2"
-><H3
-CLASS="SECT2"
-><A
-NAME="HOSTSFILE"
->4.23. Should I continue to use a <SPAN
-CLASS="QUOTE"
->"HOSTS"</SPAN
-> file for ad-blocking?</A
-></H3
-><P
-> One time-tested technique to defeat common ads is to trick the local DNS
- system by giving a phony IP address for the ad generator in the local
- <TT
-CLASS="FILENAME"
->HOSTS</TT
-> file, typically using <TT
-CLASS="LITERAL"
->127.0.0.1</TT
->, aka
- <TT
-CLASS="LITERAL"
->localhost</TT
->. This effectively blocks the ad.</P
-><P
-> There is no reason to use this technique in conjunction with
- <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
->. <SPAN
-CLASS="APPLICATION"
->Privoxy</SPAN
->
- does essentially the same thing, much more elegantly and with much more
- flexibility. A large <TT
-CLASS="FILENAME"
->HOSTS</TT
-> file, in fact, not only
- duplicates effort, but may get in the way and seriously slow down your system.
- It is recommended to remove such entries from your <TT
-CLASS="FILENAME"
->HOSTS</TT
-> file. If you think
- your hosts list is neglected by <SPAN
-CLASS="APPLICATION"
->Privoxy's </SPAN
->
- configuration, consider adding your list to your <TT
-CLASS="FILENAME"
->user.action</TT
-> file:</P
-><P
-> <TABLE
-BORDER="0"
-BGCOLOR="#E0E0E0"
-WIDTH="100%"
-><TR
-><TD
-><PRE
-CLASS="SCREEN"
-> { +block }
+# forward 127.*.*.*/ .</pre>
+ </td>
+ </tr>
+ </table>
+ <p>Unencrypted connections to systems in these address ranges will be as (un)secure as the local network is, but
+ the alternative is that your browser can't reach the network at all. Then again, that may actually be desired and
+ if you don't know for sure that your browser has to be able to reach the local network, there's no reason to
+ allow it.</p>
+ <p>If you want your browser to be able to reach servers in your local network by using their names, you will need
+ additional exceptions that look like this:</p>
+ <table border="0" bgcolor="#E0E0E0" width="100%">
+ <tr>
+ <td>
+ <pre class="SCREEN"># forward localhost/ .</pre>
+ </td>
+ </tr>
+ </table>
+ <p>Save the modified configuration file and open <a href="http://config.privoxy.org/show-status" target=
+ "_top">http://config.privoxy.org/show-status</a> in your browser, confirm that <span class=
+ "APPLICATION">Privoxy</span> has reloaded its configuration and that there are no other forward lines, unless you
+ know that you need them. If everything looks good, refer to <a href=
+ "https://wiki.torproject.org/noreply/TheOnionRouter/TorFAQ#IsMyConnectionPrivate" target="_top">Tor Faq 4.2</a>
+ to learn how to verify that you are really using <span class="APPLICATION">Tor</span>.</p>
+ <p>Afterward, please take the time to at least skim through the rest of <span class="APPLICATION">Tor's</span>
+ documentation. Make sure you understand what <span class="APPLICATION">Tor</span> does, why it is no replacement
+ for application level security, and why you probably don't want to use it for unencrypted logins.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="SITEBREAK" id="SITEBREAK">4.11. Might some things break because header information or
+ content is being altered?</a></h3>
+ <p>Definitely. It is common for sites to use browser type, browser version, HTTP header content, and various
+ other techniques in order to dynamically decide what to display and how to display it. What you see, and what I
+ see, might be very different. There are many, many ways that this can be handled, so having hard and fast rules,
+ is tricky.</p>
+ <p>The <span class="QUOTE">"User-Agent"</span> is sometimes used in this way to identify the browser, and adjust
+ content accordingly.</p>
+ <p>Also, different browsers use different encodings of non-English characters, certain web servers convert pages
+ on-the-fly according to the User Agent header. Giving a <span class="QUOTE">"User Agent"</span> with the wrong
+ operating system or browser manufacturer causes some sites in these languages to be garbled; Surfers to Eastern
+ European sites should change it to something closer. And then some page access counters work by looking at the
+ <span class="QUOTE">"Referer"</span> header; they may fail or break if unavailable. The weather maps of
+ Intellicast have been blocked by their server when no <span class="QUOTE">"Referer"</span> or cookie is provided,
+ is another example. (But you can forge both headers without giving information away). There are many other ways
+ things can go wrong when trying to fool a web server. The results of which could inadvertently cause pages to
+ load incorrectly, partially, or even not at all. And there may be no obvious clues as to just what went wrong, or
+ why. Nowhere will there be a message that says <span class="QUOTE">"<span class="emphasis"><i class=
+ "EMPHASIS">Turn off <tt class="LITERAL">fast-redirects</tt> or else!</i></span> "</span></p>
+ <p>Similar thoughts apply to modifying JavaScript, and, to a lesser degree, HTML elements.</p>
+ <p>If you have problems with a site, you will have to adjust your configuration accordingly. Cookies are probably
+ the most likely adjustment that may be required, but by no means the only one.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="CACHING" id="CACHING">4.12. Can Privoxy act as a <span class="QUOTE">"caching"</span>
+ proxy to speed up web browsing?</a></h3>
+ <p>No, it does not have this ability at all. You want something like <a href="http://www.squid-cache.org/"
+ target="_top">Squid</a> or <a href="https://www.irif.fr/~jch//software/polipo/" target="_top">Polipo</a> for
+ this. And, yes, before you ask, <span class="APPLICATION">Privoxy</span> can co-exist with other kinds of proxies
+ like <span class="APPLICATION">Squid</span>. See the <a href="../user-manual/config.html#FORWARDING" target=
+ "_top">forwarding chapter</a> in the <a href="../user-manual/index.html" target="_top">user manual</a> for
+ details.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="FIREWALL" id="FIREWALL">4.13. What about as a firewall? Can Privoxy protect
+ me?</a></h3>
+ <p>Not in the way you mean, or in the way some firewall vendors claim they can. <span class=
+ "APPLICATION">Privoxy</span> can help protect your privacy, but can't protect your system from intrusion
+ attempts. It is, of course, perfectly possible to use <span class="emphasis"><i class=
+ "EMPHASIS">both</i></span>.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="WASTED" id="WASTED">4.14. I have large empty spaces / a checkerboard pattern now where
+ ads used to be. Why?</a></h3>
+ <p>It is technically possible to eliminate banners and ads in a way that frees their allocated page space. This
+ could easily be done by blocking with <span class="APPLICATION">Privoxy's</span> filters, and eliminating the
+ <span class="emphasis"><i class="EMPHASIS">entire</i></span> image references from the HTML page source.</p>
+ <p>But, this would consume considerably more CPU resources (IOW, slow things down), would likely destroy the
+ layout of some web pages which rely on the banners utilizing a certain amount of page space, and might fail in
+ other cases, where the screen space is reserved (e.g. by HTML tables for instance). Also, making ads and banners
+ disappear without any trace complicates troubleshooting, and would sooner or later be problematic.</p>
+ <p>The better alternative is to instead let them stay, and block the resulting requests for the banners
+ themselves as is now the case. This leaves either empty space, or the familiar checkerboard pattern.</p>
+ <p>So the developers won't support this in the default configuration, but you can of course define appropriate
+ filters yourself to achieve this.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="SSL" id="SSL">4.15. How can Privoxy filter Secure (HTTPS) URLs?</a></h3>
+ <p>If you enable <a href="../user-manual/actions-file.html#HTTPS-INSPECTION" target="_top">https-inspection</a>
+ <span class="APPLICATION">Privoxy</span> will impersonate the destination server and can thus filter encrypted
+ requests and responses as well.</p>
+ <p>Without <a href="../user-manual/actions-file.html#HTTPS-INSPECTION" target="_top">https-inspection</a> secure
+ HTTP connections are encrypted SSL sessions between your browser and the secure site, and there is little that
+ <span class="APPLICATION">Privoxy</span> can do but hand the raw gibberish data though from one end to the other
+ unprocessed.</p>
+ <p>The only exception to this is blocking by host patterns, as the client needs to tell <span class=
+ "APPLICATION">Privoxy</span> the name of the remote server, so that <span class="APPLICATION">Privoxy</span> can
+ establish the connection. If that name matches a host-only pattern, the connection will be blocked.</p>
+ <p>As far as ad blocking is concerned, this is less of a restriction than it may seem, since ad sources are often
+ identifiable by the host name, and often the banners to be placed in an encrypted page come unencrypted
+ nonetheless for efficiency reasons, which exposes them to the full power of <span class=
+ "APPLICATION">Privoxy</span>'s ad blocking.</p>
+ <p><span class="QUOTE">"Content cookies"</span> (those that are embedded in the actual HTML or JS page content,
+ see <tt class="LITERAL"><a href="../user-manual/actions-file.html#FILTER-CONTENT-COOKIES" target=
+ "_top">filter{content-cookies}</a></tt>), in an SSL transaction will be impossible to block under these
+ conditions. Fortunately, this does not seem to be a very common scenario since most cookies come by traditional
+ means.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="HTTP2" id="HTTP2">4.16. Does Privoxy support HTTP/2?</a></h3>
+ <p>Privoxy currently doesn't parse HTTP/2 but applications can tunnel HTTP/2 through Privoxy if Privoxy is
+ configured to allow CONNECT requests (default) which are also used for HTTPS.</p>
+ <p>Adding HTTP/2 support is on the <a href=
+ "https://www.privoxy.org/gitweb/?p=privoxy.git;a=blob_plain;f=TODO;hb=HEAD" target="_top">TODO</a> list but
+ currently nobody is known to work on it.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="SECURE" id="SECURE">4.17. Privoxy runs as a <span class="QUOTE">"server"</span>. How
+ secure is it? Do I need to take any special precautions?</a></h3>
+ <p>On Unix-like systems, <span class="APPLICATION">Privoxy</span> can run as a non-privileged user, which is how
+ we recommend it be run. Also, by default <span class="APPLICATION">Privoxy</span> listens to requests from
+ <span class="QUOTE">"localhost"</span> only.</p>
+ <p>The server aspect of <span class="APPLICATION">Privoxy</span> is not itself directly exposed to the Internet
+ in this configuration. If you want to have <span class="APPLICATION">Privoxy</span> serve as a LAN proxy, this
+ will have to be opened up to allow for LAN requests. In this case, we'd recommend you specify only the LAN
+ gateway address, e.g. 192.168.1.1, in the main <span class="APPLICATION">Privoxy</span> configuration file and
+ check all <a href="../user-manual/config.html#ACCESS-CONTROL" target="_top">access control and security
+ options</a>. All LAN hosts can then use this as their proxy address in the browser proxy configuration, but
+ <span class="APPLICATION">Privoxy</span> will not listen on any external interfaces. ACLs can be defined in
+ addition, and using a firewall is always good too. Better safe than sorry.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="TURNOFF" id="TURNOFF">4.18. Can I temporarily disable Privoxy?</a></h3>
+ <p><span class="APPLICATION">Privoxy</span> doesn't have a transparent proxy mode, but you can toggle off
+ blocking and content filtering.</p>
+ <p>The easiest way to do that is to point your browser to the remote toggle URL: <a href=
+ "http://config.privoxy.org/toggle" target="_top">http://config.privoxy.org/toggle</a>.</p>
+ <p>See the <a href="../user-manual/appendix.html#BOOKMARKLETS" target="_top">Bookmarklets section</a> of the
+ <i class="CITETITLE">User Manual</i> for an easy way to access this feature. Note that this is a feature that may
+ need to be enabled in the main <tt class="FILENAME">config</tt> file.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="REALLYOFF" id="REALLYOFF">4.19. When <span class="QUOTE">"disabled"</span> is Privoxy
+ totally out of the picture?</a></h3>
+ <p>No, this just means all optional filtering and actions are disabled. <span class="APPLICATION">Privoxy</span>
+ is still acting as a proxy, but just doing less of the things that <span class="APPLICATION">Privoxy</span> would
+ normally be expected to do. It is still a <span class="QUOTE">"middle-man"</span> in the interaction between your
+ browser and web sites. See below to bypass the proxy.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="TURNOFF2" id="TURNOFF2">4.20. How can I tell Privoxy to totally ignore certain
+ sites?</a></h3>
+ <p>Bypassing a proxy, or proxying based on arbitrary criteria, is purely a browser configuration issue, not a
+ <span class="APPLICATION">Privoxy</span> issue. Modern browsers typically do have settings for not proxying
+ certain sites. Check your browser's help files.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="CRUNCH" id="CRUNCH">4.21. My logs show Privoxy <span class="QUOTE">"crunches"</span>
+ ads, but also its own internal CGI pages. What is a <span class="QUOTE">"crunch"</span>?</a></h3>
+ <p>A <span class="QUOTE">"crunch"</span> means <span class="APPLICATION">Privoxy</span> intercepted <span class=
+ "emphasis"><i class="EMPHASIS">something</i></span>, nothing more. Often this is indeed ads or banners, but
+ <span class="APPLICATION">Privoxy</span> uses the same mechanism for trapping requests for its own internal
+ pages. For instance, a request for <span class="APPLICATION">Privoxy's</span> configuration page at: <a href=
+ "http://config.privoxy.org" target="_top">http://config.privoxy.org</a>, is intercepted (i.e. it does not go out
+ to the 'net), and the familiar CGI configuration is returned to the browser, and the log consequently will show a
+ <span class="QUOTE">"crunch"</span>.</p>
+ <p>Since version 3.0.7, Privoxy will also log the crunch reason. If you are using an older version you might want
+ to upgrade.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="DOWNLOADS" id="DOWNLOADS">4.22. Can Privoxy affect files that I download from a
+ webserver? FTP server?</a></h3>
+ <p>From the webserver's perspective, there is no difference between viewing a document (i.e. a page), and
+ downloading a file. The same is true of <span class="APPLICATION">Privoxy</span>. If there is a match for a
+ <tt class="LITERAL"><a href="../user-manual/actions-file.html#BLOCK" target="_top">block</a></tt> pattern, it
+ will still be blocked, and of course this is obvious.</p>
+ <p>Filtering is potentially more of a concern since the results are not always so obvious, and the effects of
+ filtering are there whether the file is simply viewed, or downloaded. And potentially whether the content is some
+ obnoxious advertisement, or Mr. Jimmy's latest/greatest source code jewel. Of course, one of these presumably is
+ <span class="QUOTE">"bad"</span> content that we don't want, and the other is <span class="QUOTE">"good"</span>
+ content that we do want. <span class="APPLICATION">Privoxy</span> is blind to the differences, and can only
+ distinguish <span class="QUOTE">"good from bad"</span> by the configuration parameters <span class=
+ "emphasis"><i class="EMPHASIS">we</i></span> give it.</p>
+ <p><span class="APPLICATION">Privoxy</span> knows the differences in files according to the <span class=
+ "QUOTE">"Content Type"</span> as reported by the webserver. If this is reported accurately (e.g. <span class=
+ "QUOTE">"application/zip"</span> for a zip archive), then <span class="APPLICATION">Privoxy</span> knows to
+ ignore these where appropriate. <span class="APPLICATION">Privoxy</span> potentially can filter HTML as well as
+ plain text documents, subject to configuration parameters of course. Also, documents that are of an unknown type
+ (generally assumed to be <span class="QUOTE">"text/plain"</span>) can be filtered, as will those that might be
+ incorrectly reported by the webserver. If such a file is a downloaded file that is intended to be saved to disk,
+ then any content that might have been altered by filtering, will be saved too, for these (probably rare)
+ cases.</p>
+ <p>Note that versions later than 3.0.2 do NOT filter document types reported as <span class=
+ "QUOTE">"text/plain"</span>. Prior to this, <span class="APPLICATION">Privoxy</span> did filter this document
+ type.</p>
+ <p>In short, filtering is <span class="QUOTE">"ON"</span> if a) the content type as reported by the webserver is
+ appropriate <span class="emphasis"><i class="EMPHASIS">and</i></span> b) the configuration allows it (or at least
+ does not disallow it). That's it. There is no magic cookie anywhere to say this is <span class=
+ "QUOTE">"good"</span> and this is <span class="QUOTE">"bad"</span>. It's the configuration that lets it all
+ happen or not.</p>
+ <p>If you download text files, you probably do not want these to be filtered, particularly if the content is
+ source code, or other critical content. Source code sometimes might be mistaken for Javascript (i.e. the kind
+ that might open a pop-up window). It is recommended to turn off filtering for download sites (particularly if the
+ content may be plain text files and you are using version 3.0.2 or earlier) in your <tt class=
+ "FILENAME">user.action</tt> file. And also, for any site or page where making <span class="emphasis"><i class=
+ "EMPHASIS">any</i></span> changes at all to the content is to be avoided.</p>
+ <p><span class="APPLICATION">Privoxy</span> does not do FTP at all, only HTTP and HTTPS (SSL) protocols.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="DOWNLOADS2" id="DOWNLOADS2">4.23. I just downloaded a Perl script, and Privoxy altered
+ it! Yikes, what is wrong!</a></h3>
+ <p>Please read above.</p>
+ </div>
+ <div class="SECT2">
+ <h3 class="SECT2"><a name="HOSTSFILE" id="HOSTSFILE">4.24. Should I continue to use a <span class=
+ "QUOTE">"HOSTS"</span> file for ad-blocking?</a></h3>
+ <p>One time-tested technique to defeat common ads is to trick the local DNS system by giving a phony IP address
+ for the ad generator in the local <tt class="FILENAME">HOSTS</tt> file, typically using <tt class=
+ "LITERAL">127.0.0.1</tt>, aka <tt class="LITERAL">localhost</tt>. This effectively blocks the ad.</p>
+ <p>There is no reason to use this technique in conjunction with <span class="APPLICATION">Privoxy</span>.
+ <span class="APPLICATION">Privoxy</span> does essentially the same thing, much more elegantly and with much more
+ flexibility. A large <tt class="FILENAME">HOSTS</tt> file, in fact, not only duplicates effort, but may get in
+ the way and seriously slow down your system. It is recommended to remove such entries from your <tt class=
+ "FILENAME">HOSTS</tt> file. If you think your hosts list is neglected by <span class=
+ "APPLICATION">Privoxy's</span> configuration, consider adding your list to your <tt class=
+ "FILENAME">user.action</tt> file:</p>
+ <table border="0" bgcolor="#E0E0E0" width="100%">
+ <tr>
+ <td>
+ <pre class="SCREEN"> { +block }