An Advanced Collusion Attack against User Friendship Privacy in OSNs

Online Social Networks (OSNs) are providing a variety of applications for human users to interact with families, friends and even strangers. One of such applications, friend search engine, which allows the general public to query individual users' friend list, is gaining popularity recently. However, without proper design, this application may disclose users' private relationship information. In this paper, we propose an advanced collusion attack, where a victim user's friendship privacy setting can be compromised through a carefully designed query sequence coordinately launched by multiple malicious requstors. The effect of the proposed collusion attack is validated through synthetic social network data sets. In addition, the analysis of such advanced collusion attacks will also benefit the future design of more robust privacy preserving friend search engine in OSNs.