Mobile ad hoc network (MANET) has become an important technology in recent years because of the rapid proliferation of wireless devices. MANETs are highly vulnerable to different types of attacks due to the open medium, node mobility, lack of centralized monitoring and lack of a clear line of defense. In this paper, we propose a design of a cooperative network intrusion detection system based on Dynamic source Routing (DSR) protocol with 5 components: A context analyzer, watchdog system (monitor), rating system, alert message verifier and intruder node punishment system. This system is able to identify different types of behaviors of a misbehaving node like suspicious, malicious but not intrusive and both malicious & intrusive. Simulation result shows the effectiveness of our proposal. © 2013 IEEE.