What is MANET ?

Mobile Adhoc NETwork is a collection of mobile nodes that  dynamically form a temporary network and are capable of communicating with each other without the use of a network infrastructure or any centralized administration. 

         Due to Open medium, dynamic topology, Distributed Cooperation, Constrained Capabilities ad hoc networks are vulnerable to many types of security attacks.

                       http://en.wikipedia.org/wiki/Mobile_ad_hoc_network