  In a multi-hop mobile ad hoc network (MANET), mobile nodes cooperate to form
a network without using any infrastructure such as access points or base
stations. The mobility of the nodes and the fundamentally limited capacity of
the wireless medium, together with wireless transmission effects such as
attenuation, multi-path propagation, and interference combine to create
sig-nificant challenges for security in MANETs. Traditional cryptographic
mecha-nisms such as authentication and encryption are not capable of handling
some kinds of attacks such as packet dropping by malicious nodes in MANETs.
This paper presents a mechanism for detecting malicious packet dropping attacks
in MANETs. The mechanism is depends on a trust module on each node, which is
based on the reputation value computed for that node by its neighbors. The
reputation value of a node is computed based on its packet forwarding behavior
in the network. The reputation information is gathered, stored and exchanged
between the nodes, and computed under different scenario. The proposed
pro-tocol has been simulated in a network simulator. The simulation results
show the efficiency of its performance.
