Future wireless communication systems will be greatly dependent on the instantaneous deployment of independent mobile users. Some of the notable and interesting examples include creating sustainable, well organized, well planned, effective, and active communication systems for emergency/exigency/crises operations, catastrophe relief efforts, and military networks. Such networking situations depend on distributed, dispersed and disorganized connectivity, and can be designed as applications of Mobile Ad Hoc networks. A MANET is a self-governing and self-organizing collection of mobile nodes with relatively equal bandwidth that communicate over restricted wireless links. A MANET network is decentralized and disseminated, where all networking including topology discovery and conveying the messages must be achieved by the nodes themselves, i.e., routing capabilities are assimilated into mobile nodes. However, determining feasible routing paths for distributing messages in a decentralized network where network topology varies is a difficult job. Factors such as the open medium and vast distribution of nodes, topological changes, variable wireless link quality, and propagation path loss become pertinent issues and make MANET unprotected to intrusions. Thus, it becomes pivotal to develop a systematic intrusion detection scheme to secure Mobile Ad Hoc networks from intruders. In this paper, we put forward and applied an efficient IDS mechanism based on Enhanced Adaptive Acknowledgment (EAACK) especially made for MANETs which performs better than the previous techniques such as Watchdog, TWOACK and AACK.