Online social networks (OSNs) face various forms of fraud and attacks, such as spam, denial of service, Sybil attacks, and viral marketing. In order to build trustworthy and secure OSNs, it has become critical to develop techniques to analyze and detect OSN fraud and attacks. Existing OSN security approaches usually target a specific type of OSN fraud or attack and often fall short of detecting more complex attacks such as collusive attacks that involve many fraudulent OSN accounts, or dynamic attacks that encompass multiple attack phases over time.