An Enhanced Approach to Avoid Black hole Attack in Mobile Ad hoc Networks using AOMDV Routing Protocol

A mobile ad-hoc network (MANET) is very receptive to security attacks due to its open medium, dynamically changing network topology, lack of centralized monitoring. These vulnerabilities are nature of MANET structure that cannot be removed. As a consequence, attacks with malicious intent have been and will be devised to exploit these vulnerabilities and to cripple MANET operations. One of the well known attack on the MANET is the Black Hole attack which is most common in the ondemand routing protocols such as AODV. A black hole attack refers to an attack by a malicious node, which forcibly gains the route from a source to a destination by the falsification of sequence number and hop count of the routing message. This paper represents an enhanced AOMDV routing protocol for avoiding black hole attack in MANET. This routing protocol uses Ad hoc On-demand Multipath Distance Vector (AOMDV) to form link disjoint multi-path during path discovery to provide better path selection in order to avoid malicious nodes in the path using legitimacy table maintained by each node in the network. Nonmalicious nodes steadily isolate the black hole nodes based on the values collected in their legitimacy table and avoid them while making path between source and destination. The effectiveness of our approach is illustrated by simulations conducted using network simulator ns-2.34.