Mobile ad hoc networks (MANETs) are often prone to variety of attacks like denial of service, impersonation, eavesdropping, camouflaging adversary, blackhole, wormhole, replay, jamming, man in the middle, etc. Among all these attacks camouflaging adversary attack is the attack, launched by an insider and has a devastating effect on network performance. In this paper, we present a cognitive agents (CAs) based security scheme for identifying camouflaging adversaries in MANETs. The proposed scheme uses CAs with observations-belief model to effectively identify camouflaging adversary nodes and the identified nodes will be isolated from the network. The isolation of the camouflaged adversaries enhances the network performance with respect to various performance metrics like bandwidth, throughput, packet drop ratio, reliability, etc.