In mobile Ad hoc networks

flooding attacks will consume bandwidth and battery energy. The network connectivity will be seriously impacted. Therefore

the control and data messages can not be transmitted correctly. On the basis of introducing the basic conception of routing attack

this paper discusses the possible security threats to the Ad hoc network. A security routing mechanism based on AODV is proposed

which is composed of neighbor listening and credit standing evaluating. The computer simulations prove this mechanism can prevent the RREQ flooding attack efficiently.