In this research work, a secure routing protocol for MANET is designed with countermeasures to reduce or eliminate different types of security vulnerabilities and attacks. This thesis provides routing security to the Ad hoc On demand Distance Vector (AODV) routing protocol by eliminating the threat of Black Hole attack, Rushing attack, Wormhole attack and Impersonation attack. The proposed solutions are tested using Global Mobile system Simulator (GloMoSim), a scalable public domain network simulator. The performance is studied for various routing parameters such as packet delivery ratio; routing overhead and average end - to - end delay and are compared with the AODV. The simulation results show that the proposed solutions improve the security and packet delivery performance with lesser overhead and delay and are well suited for network with high mobility.