Network Intrusion Detection Systems (NIDS) are one of the latest developments in security. The matching of packet strings against collected signatures dominates signature-based NIDS performance. This work presents FNP², an efficient pattern-matching engine designed for Network Processor platform which conducts matching sets of patterns in parallel. This work shows that combining our string matching methodology, hashing engine supported by most Network Processors, and characteristics of current Snort signatures frequently improves performance and reduces number of memory accesses compared to current NIDS pattern matching algorithms. Another contribution is to highlight that, besides total number of searching patterns, shortest pattern length is also a major influence on NIDS multi-pattern matching algorithm performance.