-----Original Message----- From: Kraktus <krak...@googlemail.com> To: tor-talk@lists.torproject.org Sent: Mon, Apr 25, 2011 8:26 pm Subject: Re: [tor-talk] Users profiling through personаl banners filtering settings Well, you could make this argument for any blocking activity: cookies, javascript, plugins, ad-blocking, etc. If one user is blocking a bunch of things, then they stand out because they are blocking things, and most people aren't. You might even be able to do extensive tests to find out what sorts of things they are blocking and find some sort of pattern. Take cookies for example. Imagine these scenarios: 1. User blocks all cookies. 2. User blocks all cookies except cookies from whitelisted sites. 3. User accepts all cookies except cookies from blacklisted sites. 4. User accepts all cookies. Now, as I understand it, your argument is that any deviation from 4, but especially selective whitelisting/blacklisting as described in 2 and 3, is a variation from the norm and hence makes a user stand out. (I believe, it would actually either require multiple sites to collaborate to perform such an attack, or else, as you suggested, the exit node itself might perform the attack.) Now, while there are some cookies that do not contain anything unique, most cookies are used to store unique IDs. So if you accept a cookie from a site, they are probably going to give you a unique pseudonym they can use to track you with. On the other hand, if you refuse to accept cookies from that site, then you are part of the anonymity group of Tor users who do not accept cookies from that site. Yes, they could use other techniques to narrow things down, but at least you haven't let them give you a unique session ID. So, I think the closer you can get to 1, without sacrificing too much usability, the better. The more Tor users can be persuaded to do 2, the better. The more Tor users could at least be persuaded, if not to do that, then to at least have a blacklist of advertising domains (3), the better. Then you will stand out less when you refuse to accept a cookie. (In Firefox, you can use the Cookie Monster plugin to help with this.) Javascript is even worse. Javascript often has security vulnerabilities, so an attacker might exploit a buffer overflow or something, and use that to reveal your identity. Even if the Javascript is not exploited, it can still reveal a lot of information about you. For an idea of what I am talking about, take a look at this site and allow Javascript. http://ip-check.info/?lang=en (That will also show you why you shouldn't allow plugins such as Java or Flash when using Tor unless you have a fancy setup to force them through Tor, or simply don't care about your anonymity that much, and even then, they can still reveal a lot.) Now, even normal, non-exploiting Javascript still reveals much more specific information about my computer than simply "This user does not permit Javascript from your website". So again, the more Javascript you block, the better. The more Tor users can be persuaded to only allow Javascript from specific websites (where the usability concerns outweigh the anonymity concerns). the better. The more Tor users can be persuaded, if not to do that, then at least to specify websites they don't want to allow Javascript from, the better. In Firefox, NoScript can help with this. Here's a good noscript.untrusted, if you prefer the blacklist method or just want to minimize the chance of accidentally allowing javascript from an advertising/tracking domain: ad.linkstorms.com adbrite.com adbureau.net addthis.com addynamix.com adgardener.com ads.alphatrade.com ads.forbes.com ads.pointroll.com ads.reason.com ads.space.com ads1.msn.com adsonar.com adtech.de adtology3.com advertising.com adzones.com afy11.net blogads.com doubleclick.com doubleclick.net facebook.net falkag.net getclicky.com google-analytics.com googleadservices.com googlesyndication.com hitbox.com quantserve.com scorecardresearch.com serving-sys.com specificclick.net statcounter.com tacoda.net zedo.com http://adbrite.com http://adbureau.net http://addthis.com http://addynamix.com http://adgardener.com http://adsonar.com http://adtech.de http://adtology3.com http://advertising.com http://adzones.com http://afy11.net http://blogads.com http://doubleclick.net http://facebook.net http://getclicky.com http://google-analytics.com http://googleadservices.com http://googlesyndication.com http://hitbox.com http://quantserve.com http://scorecardresearch.com http://serving-sys.com http://specificclick.net http://statcounter.com http://tacoda.net http://zedo.com https://adbrite.com https://adbureau.net https://addthis.com https://addynamix.com https://adgardener.com https://adsonar.com https://adtech.de https://adtology3.com https://advertising.com https://adzones.com https://afy11.net https://blogads.com https://doubleclick.net https://facebook.net https://getclicky.com https://google-analytics.com https://googleadservices.com https://googlesyndication.com https://hitbox.com https://quantserve.com https://scorecardresearch.com https://serving-sys.com https://specificclick.net https://statcounter.com https://tacoda.net https://zedo.com I feel the same way about adblocking. The fewer web logs I show up in, the better. I don't see any reason why I should show up in the log of website that is pretty much exclusively advertising. When I visit a website, I only want to show up in the log for that website, not a bunch of third party websites. Unfortunately, some websites don't work without third-party content, so I guess unless I don't care about usability, I have to make some compromises. Still, I have found adblockplus very useful for blocking third party content without much of a usability hit. EasyList and EasyPrivacy are very helpful. The localizations are good if you visit a lot of non-English websites. Antisocial is good for stopping tracking by social networking websites. Malware Domains is probably a good idea for Windows users who don't like to use anti-virus, or who only like to use it on-demand. (That is, none of that active protection stuff.) Certain other lists are good if you are visiting certain types of websites. You know, there have been cases of people getting viruses from reputable websites when an infected advertisment somehow made it in to whatever advertiser they were using. In short, I think the privacy benefits of blocking unwanted cookies/javascript/third party content is far greater than the risk of being profiled based on your pattern of blocking stuff, and if you are concerned about being profiled based on your pattern of blocking stuff, then the solution is to get more Tor users to block more of that sort of thing. On 10/04/2011, unknown <unkn...@pgpru.com> wrote: > On Tue, 22 Mar 2011 18:26:34 +0000 > unknown <unkn...@pgpru.com> wrote: > >> Too many users dislikes of annoying web elements -- banners, popups, >> scripts, >> strange frames. They use a tools to blocks that elements or change webpage >> rendering. >> >> Traditional programs for filtering is a local proxys -- privoxy or polipo >> are examples with >> close relation to Tor and used actively. This programs cannot filtering >> SSL-content and evil site >> can use mix of SSL-ed and non-SSL-ed banners, pop-ups, etc to determine a >> fact >> of using such proxy and trying to guess personal users filtering settings. >> >> The problem may be even worse, with or without using this proxy, even if >> users block >> contents within a browser itself (with Firefox plugins to block banners, >> and scripts). Not >> only sites, but "mans in the middles", adversarial clusters of evil exit >> nodes >> can does parsing traffic and modifying web contents by injecting banners, >> misconfigured >> cookies, incorrect frames. >> >> Injected traffic for various sites, in different times >> and seances can be the way of revealing users with personal blocking >> rules. Data >> about blocking profiles of that users may be statistical processed and >> correlated. >> >> Is it a real threat? Should Tor users stop blocking contents >> selectively? Or they can use predefined and shared rules in analogy of >> Torbutton? > > Let me describe a two examples about users blocks banners in > privoxy/polipo/adblock/etc: > > 1. Webhost can see that user block russian/german/chinese/etc big portal > banners. Webservers owner can make a conjecture about specific language of > the user. > > 2. One exit or colluding exit nodes can compare banners blocking profiles > from time to time. Profiles can be linked from different seances. > > Any comments? Why does Tor Browser bundle come with Java Script enabled? > > > > _______________________________________________ > tor-talk mailing list > tor-talk@lists.torproject.org > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk > _______________________________________________ tor-talk mailing list tor-talk@lists.torproject.org https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-talk
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