Ad hoc networking refers to as network with no fixed Infrastructure. When the nodes are assumed to be capable of moving in the network, then networks are referred as MANETs (mobile ad hoc networks).Security is a paramount challenge in Ad hoc networks. Because of shared broadcast radio channels, insecure operating system, Limited resources, changing network membership, dynamic and arbitrary topology, no central authority, MANETs networks are sensitive and vulnerable to many security attacks.

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... Ts have critical application such as military applications and civilian application. In such applications, secure communication is of prime importance. Most of MANETs routing protocols works on trustworthy collaboration among participating nodes which leads to security threats. Lack of authentication and identification mechanism is another shortcoming in routing protocols due to which security issues arises in MANETs. There are many security attacks which occur on MANETs, Blackhole and Grayhole attacks being one of them. AODV protocol is effective and efficient in MANETs environment and is vulnerable to both Blackhole and Grayhole attack. A Blackhole attack is one in which malicious node falsely advertises itself as good path or stable path to destination during route discovery and malicious node starts dropping the packets instead of forwarding to destination.Grayhole attack is an extended version of the Blackhole attack where adversary behaves as a genuine node for certain time and turns into malicious node later on. In this paper, we proposed a modified version of AODV routing protocol that detect attacks before route discovery and during route discovery with high packet delivery ratio, low routing overhead and maintenance overhead.