I use firefox (mainly on linux but also on windows), and I have it set up to delete cookies and browsing history every time I exit. Despite this, every time I come to tex.stackexchange.com, I am recognized a few seconds after I connect. How is this done without cookies?
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Do you log in to a different SX site before you come to TeX.SX?– CaramdirCommented Feb 20, 2011 at 0:01
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No, it happens even if I come here first. In case it matters: I never actually log out, I just shutdown firefox.– Phil HirschhornCommented Feb 20, 2011 at 0:14
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1How do you login? Using Open Id I assume? It could be some flash based cookie which isn't deleted by firefox.– Martin ScharrerCommented Feb 20, 2011 at 0:18
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Yes, I had to create one of those OpenId thingies to register, and I seriously don't understand what that is. I've heard the phrase "flash cookie", but don't know what that is either.– Phil HirschhornCommented Feb 20, 2011 at 0:34
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I googled "flash cookies" and went to a macromedia web site that allowed me to delete all flash cookies from all sites. I then shut down firefox, started up firefox, came here, and I was still recognized. Weird...– Phil HirschhornCommented Feb 20, 2011 at 0:51
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4Actually, this should probably be asked on meta.stackoverflow.com. Why isn't there a migration path to meta.SO?– CaramdirCommented Feb 20, 2011 at 1:41
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1 Answer
Traditional browser cookies are by no means the only way to store tracking information. For example there are also cookies stored using Adobe Flash (use this site to configure flash storage).
EDIT: My original guess turns out to be wrong. They seem to use HTML5 local storage, as described in a blog post. One way to somewhat reliably remove tracking information is the BetterPrivacy Firefox addon (I haven't tested that extensively, but it seems to work for stackexchange).
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I already use noscript, so I tried blocking quantserve and google-analytics, shut down firefox, restarted firefox, came here, and it still recognized me. I'm starting to think there's someone hiding in my closet. Commented Feb 20, 2011 at 1:07
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@Phil: interestingly it does that for me now too. Anyway, as I said there are lots of methods for tracking users.– CaramdirCommented Feb 20, 2011 at 1:14
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Aha: Private Browsing. I started firefox, started private browsing, and I was not recognized here. When I turned off private browsing and returned here, I was recognized. I still wonder what's being stored where... Commented Feb 20, 2011 at 1:14
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@Phil, @Caramdir, from diveintohtml5.org/storage.html: Unlike cookies, this data is never transmitted to the remote web server (unless you go out of your way to send it manually). Commented Feb 20, 2011 at 7:05
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@Hendrik: As long as the website can access it with javascript, it can send it to any place it likes.– CaramdirCommented Feb 20, 2011 at 16:46
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@Caramdir: So you're saying the info at that link is misleading (or plain wrong)? Commented Feb 20, 2011 at 21:30
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1@Hendrik: it says '[html5 local storage] isn’t transmitted to the server', meaning that unlike a cookie it isn't sent to the server on every request. However, it must be accessible with javascript (otherwise it would be pretty useless) and it is possible to make arbitrary requests to the server using javascript (a feature that is used extensively in 'web2.0' sites). So there is nothing preventing the javascript on the site calling
example.com/tracker?id=<id from local storage>.– CaramdirCommented Feb 20, 2011 at 22:02 -
Chrome's Incognito mode by default wipes all state at session end, including HTML5 local storage. Commented Feb 21, 2011 at 9:30
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@Caramdir: Thanks for expanding. However, I'm still puzzled. Why on earth do they say "Unlike cookies, this data is never transmitted to the remote web server (unless you go out of your way to send it manually)"? I start tending to "plain wrong" ... Commented Feb 21, 2011 at 19:58
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@hendrik: it is correct from the developer point of view.– CaramdirCommented Feb 21, 2011 at 20:11