Mobile Ad hoc NETwork (MANET) is a group of mobile node communicating with each other without any infrastructure. There is no fix topology. In MANET each node works as router. All network tasks can be done by nodes. In MANET, routing will decide how the packets will be sent, received or forwarded. Main task of the multicast routing is to send data packets to group of people with minimum use of resources. As all nodes in MANET are free to move and able to join and leave the group, security is the major issue in MANET. Two types of attacks are possible in MANET- internal attack and external attack.