Black-hole and gray-hole attack are the two common attacks in a mobile ad hoc network. In black-hole attack, the adversary advertises false route information and absorbs the data traffic towards it, and finally drops all the packets. The Gray – hole attack is an improved version of the black – hole attack in which the adversary partially forwards and partially drops the packets. Its behavior cannot be predicted as it behaves normally for a certain time and late behaves maliciously. Both black-hole and gray-hole attacks disrupt the route discovery process and degrade system’s performance.
The most popular technique to detect the black-hole and gray-hole attack in a mobile ad hoc network is to monitor the behavior of nodes by a genuine node through overhearing the communication. This technique can be referred as local monitoring. Watchdog overhears the number of transmissions from a sender and router. Watchdog detects the malicious node by comparing the number of transmissions.
Solution in NS2
i) The network can be created in which some nodes are configured as attackers and some nodes are configured as watchdog nodes with detection mechanism.
ii) Attack report from the watchdog is utilized for the future network operations such as not involving those nodes in the data forwarding process or not electing those nodes as leader.
iii) Packet loss is the major performance issue due to attacker’s activity that can be traced out using trace file before and after applying the defense mechanism. Attack impact is also over the metrics such as Packet Delivery Ratio and Throughput. Delay is increased due to the retransmission of lost packets.
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