SafeCard: A Gigabit IPS on the Network Card

摘要

Current intrusion detection systems have a narrow scope. They target flow aggregates, reconstructed TCP streams, individual packets or application-level data fields, but no existing solution is capable of handling all of the above. Moreover, most systems that perform payload inspection on entire TCP streams are unable to handle gigabit link rates. We argue that network-based intrusion detection systems should consider all levels of abstraction in communication (packets, streams, layer-7 data units, and aggregates) if they are to handle gigabit link rates in the face of complex application-level attacks such as those that use evasion techniques or polymorphism. For this purpose, we developed a framework for network-based intrusion prevention at the network edge that is able to cope with all levels of abstraction and can be easily extended with new techniques. We validate our approach by making available a practical system, SafeCard, capable of reconstructing and scanning TCP streams at gigabit rates while preventing polymorphic buffer-overflow attacks, using (up to) layer-7 checks. Such performance makes it applicable in-line as an intrusion prevention system. SafeCard merges multiple solutions, some new and some known. We made specific contributions in the implementation of deep-packet inspection at high speeds and in detecting and filtering polymorphic buffer overflows.