A structure less network is called the mobile ad-hoc network, where all the nodes are independent. In MANET, there is a collection of mobile nodes that from temporary network. Those nodes are act like a host or like a router. The security issue is the main problem of MANET, because many nodes perform many kind of misbehavior. This misbehavior looks like selfishness. We can define the selfishness as, a node use the recourse of other node and preserve the resource of own. This malicious node creates the problem in MANET. In this paper, we define the attacks in MANET.