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38 >Privoxy Frequently Asked Questions</TH
46 HREF="configuration.html"
81 >4.1. How much does <SPAN
84 > slow my browsing down? This
85 has to add extra time to browsing.</A
88 > It should not slow you down any in real terms, and may actually help
89 speed things up since ads, banners and other junk are not being displayed.
90 The actual processing time required by <SPAN
94 itself for each page, is relatively small in the overall scheme of things,
95 and happens very quickly. This is typically more than offset by time saved
96 not downloading and rendering ad images.</P
101 > content via the <TT
104 HREF="../user-manual/actions-file.html#FILTER"
112 HREF="../user-manual/actions-file.html#DEANIMATE-GIFS"
117 actions may cause a perceived slowdown, since the entire document needs to be buffered
118 before displaying. See below.</P
126 >4.2. I noticed considerable
127 delays in page requests compared to the old Junkbuster. What's wrong?</A
133 HREF="../user-manual/actions-file.html#FILTER"
138 such as filtering banners by size, web-bugs etc, or the <TT
141 HREF="../user-manual/actions-file.html#DEANIMATE-GIFS"
146 action, the entire document must be loaded into memory in order for the filtering
147 mechanism to work, and nothing is sent to the browser during this time.</P
149 > The loading time does not really change in real numbers, but the feeling is
150 different, because most browsers are able to start rendering incomplete
151 content, giving the user a feeling of "it works". This effect is especially
152 noticeable on slow dialup connections.
155 > Filtering is automatically disabled for inappropriate MIME types. </P
163 >4.3. What are "http://config.privoxy.org/" and
168 HREF="http://config.privoxy.org/"
170 >http://config.privoxy.org/</A
175 >'s built-in user interface, and
180 > is a shortcut for it.</P
185 > sits between your web browser and the Internet,
186 it can simply intercept requests for these addresses and answer them with its built-in
192 > This also makes for a good test for your browser configuration: If entering the
194 HREF="http://config.privoxy.org/"
196 >http://config.privoxy.org/</A
198 takes you to a page saying <SPAN
200 >"This is Privoxy.."</SPAN
202 If you get a page saying <SPAN
204 >"Privoxy is not working"</SPAN
206 your browser didn't use <SPAN
210 hence it could not be intercepted, and you have accessed the <I
214 web site at config.privoxy.org.</P
216 > With recent versions of <SPAN
220 later), the user interface features information on the run time status, the
221 configuration, and even a built-in editor for the <A
222 HREF="../user-manual/actions-file.html"
227 > Note that the built-in URLs from earlier versions of <SPAN
234 >, http://example.com/show-proxy-args and http://i.j.b/,
235 are no longer supported. If you still use such an old version, you should really consider
236 upgrading to 2.9.18.</P
244 >4.4. Do you still maintain the blocklists?</A
247 > No. The patterns for blocking now reside (among other things) in the <A
248 HREF="../user-manual/actions-file.html"
252 actively maintained instead. See next question ...</P
260 >4.5. How can I submit new ads?</A
263 >Yes, absolutely! Please see the <A
267 how to do that. Please note that you (technically) need the latest
271 > version for this to work.</P
279 >4.6. How can I hide my IP address?</A
282 > If you run both the browser and the proxy locally, you cannot hide your IP
286 > or any other software. The
287 server needs to know your IP address to send the answers back to you. </P
289 > Fortunately there are many publicly usable anonymous proxies out there, which
290 solve the problem by providing a further level of indirection between you and
291 the web server, shared by many people, and thus letting your requests "drown"
292 in white noise of unrelated requests as far as user tracking is concerned.</P
294 > Most of them will, however, log your IP address and make it available to the
295 authorities in case you abuse that anonymity for criminal purposes. In fact
296 you can't even rule out that some of them only exist to *collect* information
297 on (those suspicious) people with a more than average preference for privacy.</P
299 > You can find a list of anonymous public proxies at <A
300 HREF="http://www.multiproxy.org/anon_list.htm"
304 more through Google. A particularly interesting project is the JAP service
305 offered by the Technical University of Dresden (<A
306 HREF="http://anon.inf.tu-dresden.de/index_en.html"
308 >http://anon.inf.tu-dresden.de/index_en.html</A
311 > There is, however, even in the single-machine case the possibility to make the
312 server believe that your machine is in fact a shared proxy serving a whole big
313 LAN, and we are looking into that.</P
324 > guarantee I am anonymous?</A
327 > No. Your chances of remaining anonymous are greatly improved, but unless you
328 are an expert on Internet security it would be safest to assume that
329 everything you do on the Web can be traced back to you.</P
334 > can remove various information about you,
338 > more freedom to decide which sites
339 you can trust, and what details you want to reveal. But it's still possible
340 that web sites can find out who you are. Here's one way this can happen.</P
342 > A few browsers disclose the user's email address in certain situations, such
343 as when transferring a file by FTP. <SPAN
347 does not filter FTP. If you need this feature, or are concerned about the
348 mail handler of your browser disclosing your email address, you might
349 consider products such as <SPAN
354 > Browsers available only as binaries could use non-standard headers to give
355 out any information they can have access to: see the manufacturer's license
356 agreement. It's impossible to anticipate and prevent every breach of privacy
357 that might occur. The professionally paranoid prefer browsers available as
358 source code, because anticipating their behavior is easier. Trust the source,
367 >4.8. Might some things break because header information or
368 content is being altered?</A
371 > Definitely. More and more sites use HTTP header content to decide what to
372 display and how to display it. There is many ways that this can be handled,
373 so having hard and fast rules, is tricky.</P
378 > in particular is often used in this way to identify
379 the browser, and adjust content accordingly. Changing this now (at least not
380 further than removing the OS information) is not recommended, since so many
381 sites do look for it. You may get undesirable results by changing this.</P
383 > For instance, different browsers use different encodings of Russian and Czech
384 characters, certain web servers convert pages on-the-fly according to the
385 User Agent header. Giving a <SPAN
389 operating system or browser manufacturer causes some sites in these languages
390 to be garbled; Surfers to Eastern European sites should change it to
391 something closer. And then some page access counters work by looking at the
395 > header; they may fail or break if unavailable. The
396 weather maps of Intellicast have been blocked by their server when no
400 > or cookie is provided, is another example. (But you
401 can forge both headers without giving information away). There are
402 many other ways things can go wrong when trying to fool a web server.</P
404 > Similar thoughts apply to modifying JavaScript, and, to a lesser degree,
407 > If you have problems with a site, you will have to adjust your configuration
408 accordingly. Cookies are probably the most likely adjustment that may
409 be required, but by no means the only one.</P
424 speed up web browsing?</A
427 > No, it does not have this ability at all. You want something like
429 HREF="http://www.squid-cache.org/"
432 > for this. And, yes,
433 before you ask, <SPAN
437 with other kinds of proxies like <SPAN
442 HREF="../user-manual/config.html#FORWARDING"
447 HREF="../user-manual/index.html"
459 >4.10. What about as a firewall? Can <SPAN
465 > Not in the way you mean, or in the way a true firewall can.
469 > can help protect your privacy, but not
470 protect you from intrusion attempts. It is, of course, perfectly possible
471 and recommended to use <I
482 >4.11. I have large empty spaces / a checkerboard pattern now where
483 ads used to be. Why?</A
486 > It would be technically possible eliminate the banners in a way that frees
487 their screen estate in many cases, by doing all banner blocking with filters,
488 i.e. eliminating the whole image references from the HTML pages instead
489 of letting them stay in, and blocking the resulting requests for the
490 banners themselves.</P
492 > But this would consume considerable CPU resources, would likely destroy
493 the layout of many web pages which rely on the banners consuming a certain
494 amount of screen space, and would fail in other cases, where the screen space
495 is reserved e.g. by tables anyway. Also, making the banners disappear without
496 a visual trace complicates troubleshooting.</P
498 > So we won't support this in the default configuration, but you can of course
499 define appropriate filters yourself.</P
510 > filter Secure (HTTPS) URLs?</A
513 > Since secure HTTP connections are encrypted SSL sessions between your browser
514 and the secure site, and are meant to be reliably <I
518 there is little that <SPAN
521 > can do but hand the raw
522 gibberish data though from one end to the other unprocessed.</P
524 > The only exception to this is blocking by host patterns, as the client needs
528 > the name of the remote server,
532 > can establish the connection.
533 If that name matches a host-only pattern, the connection will be blocked.</P
535 > As far as ad blocking is concerned, this is less of a restriction than it may
536 seem, since ad sources are often identifiable by the host name, and often
537 the banners to be placed in an encrypted page come unencrypted nonetheless
538 for efficiency reasons, which exposes them to the full power of
557 secure is it? Do I need to take any special precautions?</A
560 > There are no known exploits that might affect
564 >. On Unix-like systems,
568 > can run as a non-privileged
569 user, which is how we recommend it be run. Also, by default
573 > only listens to requests
577 > only. The server aspect of
581 > is not itself directly exposed to the
582 Internet in this configuration. If you want to have
586 > serve as a LAN proxy, this will have to
587 be opened up to allow for LAN requests. In this case, we'd recommend
588 you specify only the LAN gateway address, e.g. 192.168.1.1, in the main
592 > configuration file and check all <A
593 HREF="../user-manual/config.html#ACCESS-CONTROL"
595 >access control and security
597 >. All LAN hosts can then use this as their proxy address
598 in the browser proxy configuration, but <SPAN
602 will not listen on any external interfaces. ACLs can be defined in addition,
603 and using a firewall is always good too. Better safe than sorry.</P
611 >4.14. How can I temporarily disable <SPAN
617 > The easiest way is to access <SPAN
621 browser by using the remote toggle URL: <A
622 HREF="http://config.privoxy.org/toggle"
624 >http://config.privoxy.org/toggle</A
627 HREF="../user-manual/appendix.html#BOOKMARKLETS"
629 >Bookmarklets section</A
634 > for an easy way to access this
650 out of the picture?</A
653 > No, this just means all filtering and actions are disabled.
657 > is still acting as a proxy, but just not
658 doing any of the things that <SPAN
662 normally be expected to do. It is still a <SPAN
666 the interaction between your browser and web sites.</P
674 >4.16. Where can I find more information about <SPAN
678 and related issues?</A
681 > Other references and sites of interest to <SPAN
695 HREF="http://www.privoxy.org/"
697 >http://www.privoxy.org/</A
718 HREF="http://www.privoxy.org/faq/"
720 >http://www.privoxy.org/faq/</A
741 HREF="http://sourceforge.net/projects/ijbswa/"
743 >http://sourceforge.net/projects/ijbswa/</A
745 the Project Page for <SPAN
750 HREF="http://sourceforge.net"
769 HREF="http://config.privoxy.org/"
771 >http://config.privoxy.org/</A
773 the web-based user interface. <SPAN
777 running for this to work. Shortcut: <A
797 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());"
799 >http://www.privoxy.org/actions/</A
819 HREF="http://www.junkbusters.com/ht/en/cookies.html"
821 >http://www.junkbusters.com/ht/en/cookies.html</A
823 an explanation how cookies are used to track web users.
839 HREF="http://www.junkbusters.com/ijb.html"
841 >http://www.junkbusters.com/ijb.html</A
843 the original Internet Junkbuster.
859 HREF="http://www.waldherr.org/junkbuster/"
861 >http://www.waldherr.org/junkbuster/</A
863 Stefan Waldherr's version of Junkbuster, from which <SPAN
883 HREF="http://privacy.net/analyze/"
885 >http://privacy.net/analyze/</A
887 to check what information about you is leaked while you browse the web.
903 HREF="http://www.squid-cache.org/"
905 >http://www.squid-cache.org/</A
907 caching proxy, which is often used together with <SPAN
926 HREF="http://www.privoxy.org/developer-manual/"
928 >http://www.privoxy.org/developer-manual/</A
958 HREF="configuration.html"