Mobile Ad hoc NETwork (MANET) is one of the most important and unique applications among all the contemporary wireless networks. Also MANET does not require a fixed network infrastructure; every single node works as both a transmitter and a receiver. Nodes communicate directly with each other when they are both within the same communication range. The advantage of MANET's is its self-configuring ability of nodes which made it popular among critical mission applications like military use or emergency recovery. MANET is vulnerable to malicious attackers. In this paper, it is crucial to develop efficient intrusion-detection mechanisms to protect MANET from attacks.