MANET is a collection of number of nodes that formulates; either, a temporary or permanent, self-organized wireless network that dont rely on any pivotal central architecture or control. They are designed to use in situations where infrastructure network is either non-existent or its extremely costly to deploy. MANETs require a distinctive, unique and insistent identity for each node for its security protocols to be effective; Sybil attacks present a grave threat to such networks. We can create large number of logical identities in a Sybil attack on a single physical device by a selfish malicious node which gives a false impression to the network that they are different benign nodes and uses them to launch a harmonized attack against the network or a node. Node cooperation is very important for detection of Sybil attack, but unfortunately nodes may not always behave cooperatively and may collude in hostile environments for disrupting the detection accuracy of such systems. Sybil nodes cannot be accurately detected in the presence of malicious collusion which results in serious impact on detection accuracy of Sybil attacks. This paper proposed a novel scheme in order to detect a Sybil attack resistant to collusion by incorporating a trust based mechanism that would mitigate the benefit (the payoff gained) from collusion. Experimental results show that our proposed scheme detects Sybil or whitewashers new identities accurately and reduces the benefits of collusion in the presence of mobility.
