A MANET is considered as self administrating network in which nodes are free to come and join to communicate with various nodes. A network which has a lot of advantages for its characteristics also has disadvantage of being attacked by some malicious node. Since MANET requires that each node should posses a unique, distinct identity, Sybil attack is one of the major threat to MANET. A Sybil attack is in which a node can have different physical identity to weak the distributed MANET system. In this paper, we propose a identity mapping scheme which is implemented with the collaborative bait detection scheme for securing MANET against Sybil attack, black hole attack and gray hole attack. Approach is merged with the CBDS approach for making system more secure against various attacks. Proposed scheme is simulated on NS2 and compared with the Sybil detection scheme on various performance metrics.