In mobile ad hoc networks, a malicious node can respond with a faked route reply (RREP) message to a source that explores a route in order to make the source establish a false route leading to the malicious node. Then, the malicious node can absorb all transmitted packets like a black hole. This paper proposes a totally secure defense against the black hole attack with low control overhead and high reliability. The proposed approach, named a bullet-proof verification (BPV) method, consists of a detection phase, in which a node detects a suspicious node by analyzing the data routing information of its neighbors and a verification phase, in which a node initiates the verification of a suspicious node conditionally only if it receives RREP from the suspicious node. The crux of this approach lies in using an encrypted verification message that goes straight to the destination through the path that may include some malicious nodes and also in using both destination sequence number and hop distance for verification. In addition, a distributed watchdog mechanism is employed to track down any malicious nodes. Simulation results show that the BPV approach reduces control overhead significantly and defends against black hole attack reliably.

A mobile node in ad hoc networks may move arbitrarily and act as a router and a host simultaneously. Such a characteristic makes nodes in MANET vulnerable to potential attacks. The black hole problem, in which some malicious nodes pretend to be intermediate nodes of a route to some given destinations and drop packets that pass through it, is one of the major types of attack. In this paper, we propose a distributed and cooperative mechanism to tackle the black hole problem. The mechanism is distributed so that it suits the ad hoc nature of network, and nodes in the protocol cooperate so that they can analyze, detect, and eliminate possible multiple black-hole nodes in a more reliable fashion. Simulation results show that our method achieves a high black hole detection rate and good packet delivery rate, while the overhead is comparatively lower as the network traffic increases.