Mobile ad hoc network is infrastructure less and dynamic topology network. It is selfconfigured automatically when wireless access network is created. The nodes act as host and router which mean each node in mobile ad hoc network acts as receiver and transmitter and route packet to other nodes. In mobile ad hoc network security is challenging issue and makes the communication vulnerable to different attacks. The common type of attack in MANET is the Wormhole attack. This type of attack is dangerous attack and difficult to detect it in mobile ad-hoc networks. In wormhole attack two nodes makes a tunnel to communicate to each other as neighbour nodes or accept the data packet from sender node and drop it without sending to the destination node. The attacker nodes disturb the normal communication path by changing or dropping the packet and route path. In this thesis work an intrusion detection based on anomaly detection technique is proposed to improve the security of mobile ad-hoc network. The existing AODV routing protocol is modified to increase its security. Each mobile device in ad-hoc network is responsible to protect itself from wormhole attack. The proposed technique does not need any additional resources to configure and deploy in ad-hoc network environment. The experiment result shows that an improvement in the throughput as compared the proposed solution with the AODV routing protocol under wormhole attack.