The computer networking is increasing day by day. With the growth of computer network, e-commerce, web service computer security is very important. The detection of attacks against computer network is becoming a harder problem to solve in the field of network security. Network intrusion detection (NID) is the process of identifying network activity that can lead to the compromise of a security policy. The Fuzzy Intrusion Recognition Engine (FIRE) is a network detection system that uses fuzzy system to assess malicious activity against computer networks. This paper describes an efficient intrusion detection system with the fuzzy logic. We specify a set of fuzzy rules that can be used to detect an intrusion in the network. This paper presents the design of the FIRE system and discusses how the fuzzy agents are used to perform correlation of multiple inputs for intrusion detection. All agents communicate with a fuzzy evaluation engine that combines the results of individual agents using fuzzy rules to produce alerts that are true to a degree. We have tested our model on some data obtained from networks under simulated attacks. In this paper, we present some experimental results that indicate the fuzzy system can easily identify port scanning and unauthorized servers.