Friday, February 26, 2010

A Practical Attack to De-Anonymize Social Network Users | Gilbert Wondracek, Thorsten Holz, Engin Kirda, Sophia Antipolis, Christopher Kruegel

"Social networking sites such as Facebook, LinkedIn, and Xing have been reporting exponential growth rates. These sites have millions of registered users, and they are interesting from a security and privacy point of view because they store large amounts of sensitive personal user data. In this paper, we introduce a novel de-anonymization attack that exploits group membership information that is available on social networking sites. More precisely, we show that information about the group memberships of a user (i.e., the groups of a social network to which a user belongs) is often sufficient to uniquely identify this user, or, at least, to significantly reduce the set of possible candidates. To determine the group membership of a user, we leverage well-known web browser history stealing attacks. Thus, whenever a social network user visits a malicious website, this website can launch our de-anonymization attack and learn the identity of its visitors.

The implications of our attack are manifold, since it requires a low effort and has the potential to affect millions of social networking users. We perform both a theoretical analysis and empirical measurements to demonstrate the feasibility of our attack against Xing, a medium-sized social network with more than eight million members that is mainly used for business relationships. Our analysis suggests that about 42% of the users that use groups can be uniquely identified, while for 90%, we can reduce the candidate set to less than 2,912 persons. Furthermore, we explored other, larger social networks and performed experiments that suggest that users of Facebook and LinkedIn are equally vulnerable (although attacks would require more resources on the side of the attacker). An analysis of an additional five social networks indicates that they are also prone to our attack."

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