Mobile Ad hoc network is a constant infrastructure wireless network whose installation and use are easy and in progress. In this network, nodes in each other's radio range can directly communicate. Furthermore, this network has such properties as nature of transfer medium, finite power and energy, low bandwidth and restricted resources which facilitate intrusion to and destructive action in it. Mobile Ad hoc network does not have special defense mechanisms, resulting in the competition to give strategies and make security and intrusion detection possible. Routing is the most important problem that with this network which is done by nodes. Existence of a malicious node is a problem the routing can handle. This paper will present one new method of intrusion detection that precisely identifies malicious nodes which change the received packets or prevent them through surveying adjacent nodes in a simple way. Through this method, rate of false alarm will be reduced as simulation procedures indicate its superiority.