MANET – Mobile Adhoc Network is a self-configuring network that connected by the number of mobile nodes with wireless links and it has no fixed infrastructure. In this, each single node can operates as both a transmitter and receiver. It has been exploited in various applications such as disaster stuck areas, military, emergency revival etc. Nevertheless, the open intermediate and broad distribution of nodes in MANET can cause a vulnerable to different malicious attacks and MANET that can operate consistently even in the being there of inside packet drop attackers can be really challenging. Therefore, we need to develop Intrusion Detection System to detect the misbehavior nodes during the packet delivery with acknowledgement for the protection of MANET. In this paper, EAACK (Enhanced Adaptive Acknowledgment) is developed with Enhanced Interior Gateway Routing Protocol (EIGRP) hybrid protocol which consists of P2P ACK and RSA algorithm. At present, the network overhead is caused by the digital signature algorithm if more misbehavior nodes are presented on network. Hence, this proposed system is applied with EIGRP to reduce the network overhead caused by digital signatures in EAACK, and P2P (peer-peer) ACK and RSA (named after Ron Rivest, Adi Shamir and Len Adleman) provides more security to the network. S-ACK (Selective Acknowledgements) cannot differentiate the particular node is malicious node. Therefore, this proposed system introduces the P2P ACK to detect the misbehavior node efficiently. Here, RSA can encrypt the session key that creates the key more secure to improve the security level and P2P ACK use this encrypted key for the acknowledgement. In the P2P ACK, keys are generated by the RSA and distributed for signing and verifying the acknowledgement packets in advance. This proposed P2P ACK is used to enhance the detection of misbehavior nodes. The performance of this proposed method can improve the security level and reduce the routing overhead through the secured acknowledgement.