Many researches and telecommunication companies are looking to ad hoc networks as a promising paradigm for easy communication, especially the wireless ad hoc network for mobile hosts (e.g. MANET). Ad hoc networks require no fixed infrastructure or any kind of central servers. All nodes in ad hoc manner usually have equivalent status in the services. All the nodes in a mobile ad hoc network (MANET) are carrying out basic networking functions like packet forwarding, routing, and service discovery without the help of an established infrastructure. Nodes of an ad hoc network rely on one another in forwarding a packet to its destination, due to the limited range of each mobile host¿s wireless transmissions. Security in MANET is an essential component for basic network functions like packet forwarding and routing: network operation can be easily jeopardized if countermeasures are not embedded into basic network functions at the early stages of their design.