A memory-efficient parallel string matching for intrusion detection systems

As the variety of hazardous packet payload contents increases, the intrusion detection system (IDS) should be able to detect numerous patterns in real time. For this reason, this paper proposes an Aho-Corasick algorithm based parallel string matching. In order to balance memory usage between homogeneous finite-state machine (FSM) tiles for each string matcher, an optimal set of bit position groups is determined. Target patterns are sorted by binary-reflected gray code (BRGC), which reduces bit transitions in patterns mapped onto a string matcher. In the evaluations of Snort rules, the proposed string matching outperforms the existing bit-split string matching.