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Signature-based network intrusion detection systems (NIDSs), such as Snort and Bro, rely on a rule database that describes traffic patterns for known attacks. They examine each packets flowing through a network segment and report suspicious packets to assure security. An attack signature may be represented in terms of fields in a packet such as source/destination IP addresses, source/destination ports, protocols, specific contents in payload, etc. Typically, a Perl Compatible Regular Expression (PCRE) is used to describe a specific content in the payload which may identify an attack. Our study shows that over 60% of the execution time in an NIDS is found to perform string comparisons against a signature database of over 5,950 tokens and over 1,763 PCREs. This paper proposes to extend a bit-parallel algorithm to support multi-byte processing and PCRE. This design takes a segment of bytes from the payload of a packet and detects all possible tokens including those crossing text segment boundaries. A tool is designed to generate VHDL code from a rule set automatically. Performance results are reported.