These days, Signature based Network Intrusion Detection Systems (NIDS), which apply a set of rules to identify hostile traffic in network segments are quickly updated in order to prevent systems against new attacks. The objective of an attacker is to find out new evasion techniques to stay unseen. Unfortunately, majority of the existing techniques are based on the ambiguities of the network protocols. As a result of the emergence of the new evasion techniques, NIDS system may fail to give the correct results. The central idea of our paper is to develop a network based intrusion detection system
based on Apriori algorithm and other approaches for attack detection and test the input thus produced by the Apriori algorithm with the well known snort intrusion detection system, once candidate sets for detecting different attacks are generated. These candidates in turn will be passed as inputs to the snort intrusion detection system for detecting different attacks.