Browser sniffing has had its rogue moments, like when the Web site YouPorn was caught checking whether visitors had been to other porn sites. It turned out that YouPorn was just the top of a list of 46 Web sites that were sniffing users' browser history, according to researchers at the University of California at San Diego.
Titled "Why Johnny can't browse the Internet in Peace: On the uniqueness of Web browsing history patterns," the study's researchers examined the Web browsing history of 368,284 Internet users who visited a site that tracks their Web history and then looked at their search patterns and frequency.
Here's some explanation from the study:
Our results show that for a majority of users (69 percent), the browsing history is unique and that users for whom we could detect at least 4 visited Web sites were uniquely identified by their histories in 97 percent of cases. We observe a significant rate of stability in browser history fingerprints: for repeat visitors, 38 percent of fingerprints are identical over time...The results indicate that Web browsing histories, which can be obtained by a variety of known techniques, may be used to divulge personal preferences and interests to Web authors; as such, browsing history data can be considered similar to a biometric fingerprint.
What this all boils down to is that people are predictable in what they browse and unique at the same time. It also means that anyone sniffing users' browsing history would most likely be able to identify those same users on various Web sites. For the most part, however, major browsers have put blocks in place that prohibit browser sniffing. Still, the fact remains that Johnny really can't browse the Internet in peace.