Mobile Ad hoc network is a special peer-to-peer network that is infrastructureless

self-organizing

dynamically reconfiguration and mobile.And now people pay more attention to the using of ad hoc network in emergence area such as battle field and disaster rescue.Each node in mobile ad hoc network can be regarded as either a computer or a router

so it is very vulnerable to routing information attacks.However

little information about the security problem has been considered in the routing protocols that have been proposed.In this paper

an overview of the research about attacks against routing information is given firstly

and then we present that a security routing protocol S-DSR based on reputation systems can be used in ad hoc networks.The simulation environment and results is given and the simulation results show that S-DSR protocol can get better than DSR protocol while there exists attacking nodes.