An anonymous reader writes: The H has an article about some researchers that found a way to de-anonymize people. Compared to EFF's Panopticlick, the goal of this experiment is not to uniquely identify a user's browser, but to identify individual users. The test essentially exploits the fact that many social network users are identifiable by their membership of various groups. According to the researchers, there are very few people on any social network who belong to exactly the same groups. A "group fingerprint" can thus allow websites to identify previously anonymous visitors. They describe the setup and all details in a paper and the results look very interesting. They also have a live demo for the social network Xing that was able to de-anonymize me.