The area of ad hoc networking has been receiving increasing attention among researchers in recent years and a variety of routing protocols targeted specifically at the ad hoc networking environment have been proposed. However, little information about the effects of security exposures in terms of network performance has previously been available. This paper provides a simulation study that identifies security issues that are specific to MANET and that illustrate the effects of those threats on network performance when the DSR routing protocol is used. We focused our attention on the evaluation of network performance in terms of global throughput and delay of a mobile ad hoc network where a defined percentage of nodes behaved selfishly. The simulation study brought up two important conclusions. First, it shows that security issues have to be taken into account at the early stages of a routing protocol design. Indeed, when no countermeasures are taken, the simulation results showed that network operation and maintenance can be easily jeopardized and network performance will severely degrade. Second, a cooperative security scheme seems to be a reasonable solution to the selfishness problem: a selfish behavior can be detected through the collaboration between a number of nodes assuming that a majority of nodes do not misbehave
