Detection and removal of co-operative blackhole and grayhole attacks in MANETs

A MANET, by definition, comprises of nodes which are mobile. It has a dynamic topology and lacks a central controlling entity. These features along with undefined and unsecure boundaries make its security a very challenging issue. Blackhole and grayhole attacks can in fact seriously compromise the performance of a critical infrastructure like a MANET. In this paper we propose a mechanism to detect and remove the blackhole and grayhole attacks. The solution we are proposing tackles these attacks by maintaining an Extended Data Routing Information (EDRI) Table at each node in addition to the Routing Table of the AODV protocol. The mechanism is capable of detecting a malicious node. It also maintains a history of the node's previous malicious instances to account for the gray behaviour. Refresh packet, Renew Packet, BHID Packet, Further request and Further reply packets are also used in addition to the existing packets (RREQ and RREP). Our technique is capable of finding chain of cooperating malicious nodes which drop a significant fraction of packets.