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Comment by derekreed | Hacker News Reader

Thanks for all the insightful comments about how this "didn't work for you" or "I'm paranoid so I survived this"?

It works. It works enough of the time and on enough browsers to be very relevant to anyone who cares about the privacy/security of internet users at large.

This is an impressive proof of concept, and an important thing to be discussing, yeah?

[EDIT] To clarify, I tested this on Firefox 8.0.1 on my 2011 iMac with Lion and it worked flawlessly one by one as I visited the sites "Facebook, Reddit, Flickr", they turned from gray to green in each subsequent test.

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I don't know if it's accurate enough to be a concern. What could an attacker do with such information that is so scary? They could publish "IP address X has been to Y, Z, and W recently", or they could use it to target ads, I guess, but it doesn't seem like it's reliable enough to cause any serious harm. You could just say, "Um, no I haven't" if it becomes an issue.

It did correctly detect some sites for me, but it gave one false positive and three false negatives. With that kind of error rate I just don't see it being taken seriously in anything that matters.

You are a sample size of 1.

Read the rest of the comments here. Everyone else is having similar problems. Also, please spare me the expected "This is all anecdotal/sample size of 30" follow-up. Perhaps you can answer the real question -- is this valuable to anyone if it has a significant error margin? I think it wouldn't be allowed a margin of more than 1% if it were to be useful, and even that is kind of pushing it if you intend to do anything important with the data -- if 20 sites are tested per visitor, a 1% error rate would mean that an incorrect detection would occur every fifth visitor or so. That's enough to allow plausible deniability in my book.

FWIW, I added several improvements, and according to the built-in survey, it works for about 95% of all visitors. If you had bad results initially, clear you cache and give it a second try.

Exactly. Its a matter of spending a few hours per browser to perfect it. For all we know, someone may already have perfected it and could be using this in the wild.

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