7 CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
10 TITLE="Privoxy Frequently Asked Questions"
11 HREF="index.html"><LINK
14 HREF="configuration.html"><LINK
16 TITLE="Troubleshooting"
17 HREF="trouble.html"><LINK
20 HREF="../p_doc.css"></HEAD
31 SUMMARY="Header navigation table"
40 >Privoxy Frequently Asked Questions</TH
48 HREF="configuration.html"
86 >4.1. How much does <SPAN
89 > slow my browsing down? This
90 has to add extra time to browsing.</H3
92 > It should not slow you down any in real terms, and may actually help
93 speed things up since ads, banners and other junk are not being displayed.
94 The actual processing time required by <SPAN
98 itself for each page, is relatively small in the overall scheme of things,
99 and happens very quickly. This is typically more than offset by time saved
100 not downloading and rendering ad images.</P
105 > content via the <TT
108 HREF="../user-manual/actions-file.html#FILTER"
116 HREF="../user-manual/actions-file.html#DEANIMATE-GIFS"
121 actions may cause a perceived slowdown, since the entire document needs to be buffered
122 before displaying. See below.</P
131 >4.2. I noticed considerable
132 delays in page requests compared to the old Junkbuster. What's wrong?</H3
137 HREF="../user-manual/actions-file.html#FILTER"
142 such as filtering banners by size, web-bugs etc, or the <TT
145 HREF="../user-manual/actions-file.html#DEANIMATE-GIFS"
150 action, the entire document must be loaded into memory in order for the filtering
151 mechanism to work, and nothing is sent to the browser during this time.</P
153 > The loading time does not really change in real numbers, but the feeling is
154 different, because most browsers are able to start rendering incomplete
155 content, giving the user a feeling of "it works". This effect is especially
156 noticeable on slow dialup connections.
159 > Filtering is automatically disabled for inappropriate MIME types. </P
168 >4.3. What are "http://config.privoxy.org/" and
172 HREF="http://config.privoxy.org/"
174 >http://config.privoxy.org/</A
179 >'s built-in user interface, and
184 > is a shortcut for it.</P
189 > sits between your web browser and the Internet,
190 it can simply intercept requests for these addresses and answer them with its built-in
196 > This also makes for a good test for your browser configuration: If entering the
198 HREF="http://config.privoxy.org/"
200 >http://config.privoxy.org/</A
202 takes you to a page saying <SPAN
204 >"This is Privoxy ..."</SPAN
206 If you get a page saying <SPAN
208 >"Privoxy is not working"</SPAN
210 your browser didn't use <SPAN
214 hence it could not be intercepted, and you have accessed the <SPAN
221 web site at config.privoxy.org.</P
223 > With recent versions of <SPAN
227 later), the user interface features information on the run time status, the
228 configuration, and even a built-in editor for the <A
229 HREF="../user-manual/actions-file.html"
234 > Note that the built-in URLs from earlier versions of <SPAN
241 >, http://example.com/show-proxy-args and http://i.j.b/,
242 are no longer supported. If you still use such an old version, you should really consider
243 upgrading to 0.0.0.</P
252 >4.4. Do you still maintain the blocklists?</H3
254 > No. The patterns for blocking now reside (among other things) in the <A
255 HREF="../user-manual/actions-file.html"
259 actively maintained instead. See next question ...</P
268 >4.5. How can I submit new ads?</H3
270 >Yes, absolutely! Please see the <A
274 how to do that. Please note that you (technically) need the latest
278 > version for this to work.</P
287 >4.6. How can I hide my IP address?</H3
289 > If you run both the browser and the proxy locally, you cannot hide your IP
293 > or any other software. The
294 server needs to know your IP address to send the answers back to you. </P
296 > Fortunately there are many publicly usable anonymous proxies out there, which
297 solve the problem by providing a further level of indirection between you and
298 the web server, shared by many people, and thus letting your requests "drown"
299 in white noise of unrelated requests as far as user tracking is concerned.</P
301 > Most of them will, however, log your IP address and make it available to the
302 authorities in case you abuse that anonymity for criminal purposes. In fact
303 you can't even rule out that some of them only exist to *collect* information
304 on (those suspicious) people with a more than average preference for privacy.</P
306 > You can find a list of anonymous public proxies at <A
307 HREF="http://www.multiproxy.org/anon_list.htm"
311 more through Google. A particularly interesting project is the JAP service
312 offered by the Technical University of Dresden (<A
313 HREF="http://anon.inf.tu-dresden.de/index_en.html"
315 >http://anon.inf.tu-dresden.de/index_en.html</A
318 > There is, however, even in the single-machine case the possibility to make the
319 server believe that your machine is in fact a shared proxy serving a whole big
320 LAN, and we are looking into that.</P
332 > guarantee I am anonymous?</H3
334 > No. Your chances of remaining anonymous are greatly improved, but unless you
335 are an expert on Internet security it would be safest to assume that
336 everything you do on the Web can be traced back to you.</P
341 > can remove various information about you,
348 > more freedom to decide which sites
349 you can trust, and what details you want to reveal. But it's still possible
350 that web sites can find out who you are. Here's one way this can happen.</P
352 > A few browsers disclose the user's email address in certain situations, such
353 as when transferring a file by FTP. <SPAN
357 does not filter FTP. If you need this feature, or are concerned about the
358 mail handler of your browser disclosing your email address, you might
359 consider products such as <SPAN
364 > Browsers available only as binaries could use non-standard headers to give
365 out any information they can have access to: see the manufacturer's license
366 agreement. It's impossible to anticipate and prevent every breach of privacy
367 that might occur. The professionally paranoid prefer browsers available as
368 source code, because anticipating their behavior is easier. Trust the source,
378 >4.8. Might some things break because header information or
379 content is being altered?</H3
381 > Definitely. More and more sites use HTTP header content to decide what to
382 display and how to display it. There is many ways that this can be handled,
383 so having hard and fast rules, is tricky.</P
388 > in particular is often used in this way to identify
389 the browser, and adjust content accordingly. Changing this now (at least not
390 further than removing the OS information) is not recommended, since so many
391 sites do look for it. You may get undesirable results by changing this.</P
393 > For instance, different browsers use different encodings of Russian and Czech
394 characters, certain web servers convert pages on-the-fly according to the
395 User Agent header. Giving a <SPAN
399 operating system or browser manufacturer causes some sites in these languages
400 to be garbled; Surfers to Eastern European sites should change it to
401 something closer. And then some page access counters work by looking at the
405 > header; they may fail or break if unavailable. The
406 weather maps of Intellicast have been blocked by their server when no
410 > or cookie is provided, is another example. (But you
411 can forge both headers without giving information away). There are
412 many other ways things can go wrong when trying to fool a web server.</P
414 > Similar thoughts apply to modifying JavaScript, and, to a lesser degree,
417 > If you have problems with a site, you will have to adjust your configuration
418 accordingly. Cookies are probably the most likely adjustment that may
419 be required, but by no means the only one.</P
435 speed up web browsing?</H3
437 > No, it does not have this ability at all. You want something like
439 HREF="http://www.squid-cache.org/"
442 > for this. And, yes,
443 before you ask, <SPAN
447 with other kinds of proxies like <SPAN
452 HREF="../user-manual/config.html#FORWARDING"
457 HREF="../user-manual/index.html"
470 >4.10. What about as a firewall? Can <SPAN
475 > Not in the way you mean, or in the way a true firewall can.
479 > can help protect your privacy, but not
480 protect you from intrusion attempts. It is, of course, perfectly possible
481 and recommended to use <SPAN
496 >4.11. I have large empty spaces / a checkerboard pattern now where
497 ads used to be. Why?</H3
499 > It would be technically possible eliminate the banners in a way that frees
500 their screen estate in many cases, by doing all banner blocking with filters,
501 i.e. eliminating the whole image references from the HTML pages instead
502 of letting them stay in, and blocking the resulting requests for the
503 banners themselves.</P
505 > But this would consume considerable CPU resources, would likely destroy
506 the layout of many web pages which rely on the banners consuming a certain
507 amount of screen space, and would fail in other cases, where the screen space
508 is reserved e.g. by tables anyway. Also, making the banners disappear without
509 a visual trace complicates troubleshooting.</P
511 > So we won't support this in the default configuration, but you can of course
512 define appropriate filters yourself.</P
524 > filter Secure (HTTPS) URLs?</H3
526 > Since secure HTTP connections are encrypted SSL sessions between your browser
527 and the secure site, and are meant to be reliably <SPAN
534 there is little that <SPAN
537 > can do but hand the raw
538 gibberish data though from one end to the other unprocessed.</P
540 > The only exception to this is blocking by host patterns, as the client needs
544 > the name of the remote server,
548 > can establish the connection.
549 If that name matches a host-only pattern, the connection will be blocked.</P
551 > As far as ad blocking is concerned, this is less of a restriction than it may
552 seem, since ad sources are often identifiable by the host name, and often
553 the banners to be placed in an encrypted page come unencrypted nonetheless
554 for efficiency reasons, which exposes them to the full power of
562 >"Content cookies"</SPAN
563 > (those that are embedded in the actual HTML or
564 JS page content, see <TT
567 HREF="../user-manual/actions-file.html#FILTER-CONTENT-COOKIES"
569 >filter{content-cookies}</A
572 in an SSL transaction will be impossible to block under these conditions.
573 Fortunately, this does not seem to be a very common scenario since most
574 cookies come by traditional means.</P
590 secure is it? Do I need to take any special precautions?</H3
592 > There are no known exploits that might affect
596 >. On Unix-like systems,
600 > can run as a non-privileged
601 user, which is how we recommend it be run. Also, by default
605 > only listens to requests
609 > only. The server aspect of
613 > is not itself directly exposed to the
614 Internet in this configuration. If you want to have
618 > serve as a LAN proxy, this will have to
619 be opened up to allow for LAN requests. In this case, we'd recommend
620 you specify only the LAN gateway address, e.g. 192.168.1.1, in the main
624 > configuration file and check all <A
625 HREF="../user-manual/config.html#ACCESS-CONTROL"
627 >access control and security
629 >. All LAN hosts can then use this as their proxy address
630 in the browser proxy configuration, but <SPAN
634 will not listen on any external interfaces. ACLs can be defined in addition,
635 and using a firewall is always good too. Better safe than sorry.</P
644 >4.14. How can I temporarily disable <SPAN
649 > The easiest way is to access <SPAN
653 browser by using the remote toggle URL: <A
654 HREF="http://config.privoxy.org/toggle"
656 >http://config.privoxy.org/toggle</A
659 HREF="../user-manual/appendix.html#BOOKMARKLETS"
661 >Bookmarklets section</A
666 > for an easy way to access this
683 out of the picture?</H3
685 > No, this just means all filtering and actions are disabled.
689 > is still acting as a proxy, but just not
690 doing any of the things that <SPAN
694 normally be expected to do. It is still a <SPAN
698 the interaction between your browser and web sites.</P
707 >4.16. My logs show <SPAN
714 ads, but also its own CGI pages. What is a <SPAN
732 >, nothing more. Often this is indeed ads or
736 > uses the same mechanism for
737 trapping requests for its own internal pages. For instance, a request for
741 > configuration page at: <A
742 HREF="http://config.privoxy.org"
744 >http://config.privoxy.org</A
746 intercepted (i.e. it does not go out to the 'net), and the familiar CGI
747 configuration is returned to the browser, and the log consequently will show
763 > effect files that I download
764 from a webserver? FTP server?</H3
766 > From the webserver's perspective, there is no difference between
767 viewing a document (i.e. a page), and downloading a file. The same is true of
771 >. If there is a match for a <TT
774 HREF="../user-manual/actions-file.html#BLOCK"
779 it will still be blocked, and of course this is obvious. Filtering is
780 potentially more of a concern since the results are not always so obvious.</P
785 > knows the differences in files according
788 >"Document Type"</SPAN
789 > as reported by the webserver. If this is
790 reported accurately (e.g. <SPAN
792 >"application/zip"</SPAN
793 > for a zip archive),
797 > knows to ignore these where
798 appropriate. It is possible, however, that documents that are of an unknown
799 type (generally assumed to be <SPAN
802 >) will be filtered, as
803 will those that might be incorrectly reported by the webserver. If such a
804 file is a downloaded file that is intended to be saved to disk, then any
805 content that might have been altered by filtering, will be saved too, for
806 these (probably very rare) cases.</P
811 > does not do FTP at all, only HTTP
821 >4.18. Where can I find more information about <SPAN
825 and related issues?</H3
827 > Other references and sites of interest to <SPAN
841 HREF="http://www.privoxy.org/"
843 >http://www.privoxy.org/</A
864 HREF="http://www.privoxy.org/faq/"
866 >http://www.privoxy.org/faq/</A
887 HREF="http://sourceforge.net/projects/ijbswa/"
889 >http://sourceforge.net/projects/ijbswa/</A
891 the Project Page for <SPAN
896 HREF="http://sourceforge.net"
915 HREF="http://config.privoxy.org/"
917 >http://config.privoxy.org/</A
919 the web-based user interface. <SPAN
923 running for this to work. Shortcut: <A
943 HREF="javascript:w=Math.floor(screen.width/2);h=Math.floor(screen.height*0.9);void(window.open('http://www.privoxy.org/actions','Feedback','screenx='+w+',width='+w+',height='+h+',scrollbars=yes,toolbar=no,location=no,directories=no,status=no,menubar=no,copyhistory=no').focus());"
945 >http://www.privoxy.org/actions/</A
965 HREF="http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/ijbswa/contrib/"
967 >http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/ijbswa/contrib/</A
969 and fun ideas from <SPAN
988 HREF="http://www.junkbusters.com/ht/en/cookies.html"
990 >http://www.junkbusters.com/ht/en/cookies.html</A
992 an explanation how cookies are used to track web users.
1008 HREF="http://www.junkbusters.com/ijb.html"
1010 >http://www.junkbusters.com/ijb.html</A
1012 the original Internet Junkbuster.
1028 HREF="http://www.waldherr.org/junkbuster/"
1030 >http://www.waldherr.org/junkbuster/</A
1032 Stefan Waldherr's version of Junkbuster, from which <SPAN
1052 HREF="http://privacy.net/analyze/"
1054 >http://privacy.net/analyze/</A
1056 to check what information about you is leaked while you browse the web.
1072 HREF="http://www.squid-cache.org/"
1074 >http://www.squid-cache.org/</A
1076 caching proxy, which is often used together with <SPAN
1095 HREF="http://www.privoxy.org/developer-manual/"
1097 >http://www.privoxy.org/developer-manual/</A
1118 >4.19. I've noticed that Privoxy changes <SPAN
1125 >! Why are you manipulating my browsing?</H3
1127 > We're not. The text substitutions that you are seeing are disabled
1128 in the default configuration as shipped. You have either manually
1136 is clearly labeled <SPAN
1138 >"Text replacements for subversive browsing
1140 > or you have implicitly activated it by choosing the
1144 > profile in the web-based editor (formerly known
1156 SUMMARY="Footer navigation table"
1167 HREF="configuration.html"
1205 >Troubleshooting</TD