In The 5th ACM International Conference on Distributed Event-Based Systems (DEBS), pages 171-182, July 2011.
Computer systems continue to be breached despite substantial investments in defense mechanisms to stop attacks from propagating. The accuracy of current intrusion detection systems (IDSes) is hindered by the limited capability of regular expressions (REs) to express the exact vulnerability. Recent advances have proposed vulnerability-based IDSes that parse traffic and retrieve protocol semantics to describe the vulnerability. Such a description of attacks is analogous to subscriptions that specify events of interest in event processing systems. However, the matching engine of state-of-the-art IDSes lacks efficient matching algorithms that can process many signatures simultaneously. In this work, we place event processing in the core of the IDS and propose novel algorithms to efficiently match vulnerability signatures. Also, we are among the first to detect complex attacks such as the Conficker worm which requires correlating multiple protocol data units (MPDUs) while maintaining a small memory footprint. Finally, we show that our algorithms are resilient to attacks through extensive testing of the IDS under different workloads. Our approach incurs negligible overhead when processing clean traffic and is faster than existing systems.