Detection of gray hole in MANET through cluster analysis

Mobile Ad-Hoc Networks are autonomous and decentralized wireless systems. MANETs consist of mobile nodes that are free in moving in and out in the network. Security in Mobile Ad-Hoc Network is the most important concern for the basic functionality of network. MANETs often suffer from security attacks because of its features like open medium, changing its topology dynamically, lack of central monitoring and management, cooperative algorithms and no clear defense mechanism. This characteristic makes MANETs more vulnerable to be exploited by an attacker inside the network. In MANET, a gray hole refers to a malicious node which initially responds to route requests normally but when packets are sent to it for transmission, it drops those packets either selectively or indiscriminately. In terms of detection, a gray hole is harder to detect since it behaves normally during the route discovery phase. Its malicious behavior exhibits only when data packets are routed through it. This behavior can be intermittent and not necessarily continuous or periodic in nature. This paper speaks about gray hole detection by using cluster of three nodes and its performance with various mobility and number of nodes.