Abstract: In a network intrusion detection system, the original AC algorithm adopts oncway matching. I}he comparing time will increase as the number of samples increases. This paper presented an efficient multi-pattern matching algorithm,a bi-directional fast string matching algorithm. The algorithm uses finite automata and forward-backward twoway matching. Compared with the original oncway matching algorithm, the intrusion detection rate is increased by 3 times. The performance of the algorithm was analyzed and compared with other algorithms. Simulation results show that this algorithm can improve the efficiency and detection rate.

Key words: Ad hoc network, Intrusion detection, Pattern matching, RcAC algorithm