Cooperative Security Agents for MANET

A mobile ad hoc network (MANET) is a collection of autonomous nodes that communicate with each other by forming a multi-hop radio network and maintaining connections in a decentralized manner. Security remains a major challenge for these networks due to their features of open medium, dynamically changing topologies, reliance on cooperative algorithms, absence of centralized monitoring points, and lack of clear lines of defence. Ad hoc on-demand distance vector routing (AODV) is a very popular routing algorithm, they enables dynamic, self-starting, multi hop routing between participating mobile nodes wishing to establish and maintain an Ad Hoc network. An intermediate node, which takes part in packets forwarding, may behave maliciously and drop packets which goes through it, instead of forwarding them to the following node, where a malicious node falsely advertises good paths to a destination node during the route discovery process, such behavior is called blackhole attack. This attack becomes more sever when a group of malicious nodes cooperate to each other. However, it is vulnerable to the well-known cooperative blackhole attack. In this paper, a Detecting mechanism is presented against a coordinated attack by cooperative blackhole nodes in a MANET plus a method to secure the history records of packet delivery information at each contact so that other nodes can detect insider attacks (grayhole attack) by analyzing these packet delivery records and avoid the blackhole and the cooperative blackhole attacks by using Cooperative Security Agents.