The recent and rapid advancements in the technology and the distinct features of MANETs have made the use of MANETs more prevalent. With the ever increasing applications, the weakness of these networks against a variety of attacks has been unveiled. MANETs doesn't have clear and efficient mechanisms to detect or prevent the attacks, so attacker node can easily interrupt and destroy the whole system or may take control over the information being transmitted in the network. Attackers introduce various kinds of attacks and every attack has its own degree of impact on the network. Security is a major concern in MANETs because of its intrinsic vulnerabilities.