Intrusion Detection Systems (IDSs) are known as useful tools for identifying malicious attempts over the network. The most essential part to an IDS is the searching engine that inspects every packet through the network. To strictly defend the protectorate, an IDS must be able to inspect packets at line rate and also provide guaranteed performance even under heavy attacks. Therefore, in this paper we propose an efficient string matching algorithm (named ACM) with compact memory as well as high

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... rst-case performance. Using a magic number heuristic based on the Chinese Remainder Theorem, the proposed ACM significantly reduces the memory requirement without bringing complex processes. Furthermore, the latency of off-chip memory references is drastically reduced. The proposed ACM can be easily implemented in hardware and software. As a result, ACM enables cost-effective and efficient IDSs.