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40 >Privoxy Frequently Asked Questions</TH
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76 NAME="MISC">4. Miscellaneous</H1
82 NAME="AEN504">4.1. How much does <SPAN
85 > slow my browsing down? This
86 has to add extra time to browsing.</H3
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
125 NAME="LOADINGTIMES">4.2. I noticed considerable
126 delays in page requests compared to the old Junkbuster. What's wrong?</H3
131 HREF="../user-manual/actions-file.html#FILTER"
136 such as filtering banners by size, web-bugs etc, or the <TT
139 HREF="../user-manual/actions-file.html#DEANIMATE-GIFS"
144 action, the entire document must be loaded into memory in order for the filtering
145 mechanism to work, and nothing is sent to the browser during this time.</P
147 > The loading time does not really change in real numbers, but the feeling is
148 different, because most browsers are able to start rendering incomplete
149 content, giving the user a feeling of "it works". This effect is especially
150 noticeable on slow dialup connections.
158 NAME="CONFIGURL">4.3. What are "http://config.privoxy.org/" and
162 HREF="http://config.privoxy.org/"
164 >http://config.privoxy.org/</A
169 >'s built-in user interface, and
174 > is a shortcut for it.</P
179 > sits between your web browser and the Internet,
180 it can simply intercept requests for these addresses and answer them with its built-in
186 > This also makes for a good test for your browser configuration: If entering the
188 HREF="http://config.privoxy.org/"
190 >http://config.privoxy.org/</A
192 takes you to a page saying <SPAN
194 >"This is Privoxy.."</SPAN
196 If you get a page saying <SPAN
198 >"Privoxy is not working"</SPAN
200 your browser didn't use <SPAN
204 hence it could not be intercepted, and you have accessed the <SPAN
211 web site at config.privoxy.org.</P
213 > With recent versions of <SPAN
217 later), the user interface features information on the run time status, the
218 configuration, and even a built-in editor for the <A
219 HREF="../user-manual/actions-file.html"
224 > Note that the built-in URLs from earlier versions of <SPAN
231 >, http://example.com/show-proxy-args and http://i.j.b/,
232 are no longer supported. If you still use such an old version, you should really consider
233 upgrading to 2.9.15.</P
240 NAME="BLOCKLIST">4.4. Do you still maintain the blocklists?</H3
242 > No. The patterns for blocking now reside (among other things) in the <A
243 HREF="../user-manual/actions-file.html"
247 actively maintained instead. See next question ...</P
254 NAME="NEWADS">4.5. How can I submit new ads?</H3
256 >Yes, absolutely! Please see the <A
260 how to do that. Please note that you (technically) need the latest
264 > version for this to work.</P
271 NAME="IP">4.6. How can I hide my IP address?</H3
273 > If you run both the browser and the proxy locally, you cannot hide your IP
277 > or any other software. The
278 server needs to know your IP address to send the answers back to you. </P
280 > Fortunately there are many publicly usable anonymous proxies out there, which
281 solve the problem by providing a further level of indirection between you and
282 the web server, shared by many people, and thus letting your requests "drown"
283 in white noise of unrelated requests as far as user tracking is concerned.</P
285 > Most of them will, however, log your IP address and make it available to the
286 authorities in case you abuse that anonymity for criminal purposes. In fact
287 you can't even rule out that some of them only exist to *collect* information
288 on (those suspicious) people with a more than average preference for privacy.</P
290 > You can find a list of anonymous public proxies at <A
291 HREF="http://www.multiproxy.org/anon_list.htm"
295 more through Google. A particularly interesting project is the JAP service
296 offered by the Technical University of Dresden (<A
297 HREF="http://anon.inf.tu-dresden.de/index_en.html"
299 >http://anon.inf.tu-dresden.de/index_en.html</A
302 > There is, however, even in the single-machine case the possibility to make the
303 server believe that your machine is in fact a shared proxy serving a whole big
304 LAN, and we are looking into that.</P
311 NAME="AEN563">4.7. Can <SPAN
314 > guarantee I am anonymous?</H3
316 > No. Your chances of remaining anonymous are greatly improved, but unless you
317 are an expert on Internet security it would be safest to assume that
318 everything you do on the Web can be traced back to you.</P
323 > can remove various information about you,
330 > more freedom to decide which sites
331 you can trust, and what details you want to reveal. But it's still possible
332 that web sites can find out who you are. Here's one way this can happen.</P
334 > A few browsers disclose the user's email address in certain situations, such
335 as when transferring a file by FTP. <SPAN
339 does not filter FTP. If you need this feature, or are concerned about the
340 mail handler of your browser disclosing your email address, you might
341 consider products such as <SPAN
346 > Browsers available only as binaries could use non-standard headers to give
347 out any information they can have access to: see the manufacturer's license
348 agreement. It's impossible to anticipate and prevent every breach of privacy
349 that might occur. The professionally paranoid prefer browsers available as
350 source code, because anticipating their behavior is easier. Trust the source,
358 NAME="AEN574">4.8. Might some things break because header information or
359 content is being altered?</H3
361 > Definitely. More and more sites use HTTP header content to decide what to
362 display and how to display it. There is many ways that this can be handled,
363 so having hard and fast rules, is tricky.</P
368 > in particular is often used in this way to identify
369 the browser, and adjust content accordingly. Changing this now (at least not
370 further than removing the OS information) is not recommended, since so many
371 sites do look for it. You may get undesirable results by changing this.</P
373 > For instance, different browsers use different encodings of Russian and Czech
374 characters, certain web servers convert pages on-the-fly according to the
375 User Agent header. Giving a <SPAN
379 operating system or browser manufacturer causes some sites in these languages
380 to be garbled; Surfers to Eastern European sites should change it to
381 something closer. And then some page access counters work by looking at the
385 > header; they may fail or break if unavailable. The
386 weather maps of Intellicast have been blocked by their server when no
390 > or cookie is provided, is another example. (But you
391 can forge both headers without giving information away). There are
392 many other ways things can go wrong when trying to fool a web server.</P
394 > Similar thoughts apply to modifying JavaScript, and, to a lesser degree,
397 > If you have problems with a site, you will have to adjust your configuration
398 accordingly. Cookies are probably the most likely adjustment that may
399 be required, but by no means the only one.</P
406 NAME="AEN585">4.9. Can <SPAN
413 speed up web browsing?</H3
415 > No, it does not have this ability at all. You want something like
417 HREF="http://www.squid-cache.org/"
420 > for this. And, yes,
421 before you ask, <SPAN
425 with other kinds of proxies like <SPAN
430 HREF="../user-manual/config.html#FORWARDING"
435 HREF="../user-manual/index.html"
446 NAME="AEN595">4.10. What about as a firewall? Can <SPAN
451 > Not in the way you mean, or in the way a true firewall can.
455 > can help protect your privacy, but not
456 protect you from intrusion attempts. It is, of course, perfectly possible
457 and recommended to use <SPAN
470 NAME="AEN601">4.11. I have large empty spaces / a checkerboard pattern now where
471 ads used to be. Why?</H3
473 > It would be technically possible eliminate the banners in a way that frees
474 their screen estate in many cases, by doing all banner blocking with filters,
475 i.e. eliminating the whole image references from the HTML pages instead
476 of letting them stay in, and blocking the resulting requests for the
477 banners themselves.</P
479 > But this would consume considerable CPU resources, would likely destroy
480 the layout of many web pages which rely on the banners consuming a certain
481 amount of screen space, and would fail in other cases, where the screen space
482 is reserved e.g. by tables anyway. Also, making the banners disappear without
483 a visual trace complicates troubleshooting.</P
485 > So we won't support this in the default configuration, but you can of course
486 define appropriate filters yourself.</P
493 NAME="AEN606">4.12. How can <SPAN
496 > filter Secure (HTTPS) URLs?</H3
498 > Since secure HTTP connections are encrypted SSL sessions between your browser
499 and the secure site, and are meant to be reliably <SPAN
506 there is little that <SPAN
509 > can do but hand the raw
510 gibberish data though from one end to the other unprocessed.</P
512 > The only exception to this is blocking by host patterns, as the client needs
516 > the name of the remote server,
520 > can establish the connection.
521 If that name matches a host-only pattern, the connection will be blocked.</P
523 > As far as ad blocking is concerned, this is less of a restriction than it may
524 seem, since ad sources are often identifiable by the host name, and often
525 the banners to be placed in an encrypted page come unencrypted nonetheless
526 for efficiency reasons, which exposes them to the full power of
537 NAME="AEN617">4.13. <SPAN
544 secure is it? Do I need to take any special precautions?</H3
546 > There are no known exploits that might affect
550 >. On Unix-like systems,
554 > can run as a non-privileged
555 user, which is how we recommend it be run. Also, by default
559 > only listens to requests
563 > only. The server aspect of
567 > is not itself directly exposed to the
568 Internet in this configuration. If you want to have
572 > serve as a LAN proxy, this will have to
573 be opened up to allow for LAN requests. In this case, we'd recommend
574 you specify only the LAN gateway address, e.g. 192.168.1.1, in the main
578 > configuration file and check all <A
579 HREF="../user-manual/config.html#ACCESS-CONTROL"
581 >access control and security
583 >. All LAN hosts can then use this as their proxy address
584 in the browser proxy configuration, but <SPAN
588 will not listen on any external interfaces. ACLs can be defined in addition,
589 and using a firewall is always good too. Better safe than sorry.</P
596 NAME="TURNOFF">4.14. How can I temporarily disable <SPAN
601 > The easiest way is to access <SPAN
605 browser by using the remote toggle URL: <A
606 HREF="http://config.privoxy.org/toggle"
608 >http://config.privoxy.org/toggle</A
616 NAME="SEEALSO">4.15. Where can I find more information about <SPAN
620 and related issues?</H3
622 > Other references and sites of interest to <SPAN
636 HREF="http://www.privoxy.org/"
638 >http://www.privoxy.org/</A
659 HREF="http://www.privoxy.org/faq/"
661 >http://www.privoxy.org/faq/</A
682 HREF="http://sourceforge.net/projects/ijbswa/"
684 >http://sourceforge.net/projects/ijbswa/</A
686 the Project Page for <SPAN
691 HREF="http://sourceforge.net"
710 HREF="http://config.privoxy.org/"
712 >http://config.privoxy.org/</A
714 the web-based user interface. <SPAN
718 running for this to work. Shortcut: <A
738 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());"
740 >http://www.privoxy.org/actions/</A
760 HREF="http://www.junkbusters.com/ht/en/cookies.html"
762 >http://www.junkbusters.com/ht/en/cookies.html</A
764 an explanation how cookies are used to track web users.
780 HREF="http://www.junkbusters.com/ijb.html"
782 >http://www.junkbusters.com/ijb.html</A
784 the original Internet Junkbuster.
800 HREF="http://www.waldherr.org/junkbuster/"
802 >http://www.waldherr.org/junkbuster/</A
804 Stefan Waldherr's version of Junkbuster, from which <SPAN
824 HREF="http://privacy.net/analyze/"
826 >http://privacy.net/analyze/</A
828 to check what information about you is leaked while you browse the web.
844 HREF="http://www.squid-cache.org/"
846 >http://www.squid-cache.org/</A
848 caching proxy, which is often used together with <SPAN
867 HREF="http://www.privoxy.org/developer-manual/"
869 >http://www.privoxy.org/developer-manual/</A
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