The hegira to wireless network from wired network has been a worldwide trend in the past few years. The mobility and scalability brought by a wireless network made it possible in many applications. Mobile Ad Hoc Network (MANET) is one of the most predominant and idiosyncratic applications. On the contrary to accustomed network architecture, MANET does not require a fixed network infrastructure, every single node works as Transceiver. Nodes communicate directly with each other when they are both within the same communication range. Otherwise, they reckon on their neighbors to relay messages. The Self-configuring ability of nodes in MANET made it popular among critical mission applications like military use or emergency recovery. However, the open medium and wide distribution of nodes make MANET impuissant to rancorous attackers. In this case, it is pivotal to develop efficient encroachment-detection mechanisms to protect MANET from attacks. To adjust to such trend, we strongly believe that it is vital to address its potential security issues. In this paper, the authors have proposed and implemented a new encroachment-detection system named Enhanced Double Acknowledgment (EDACK) specially designed for MANET. Compared to various approaches, EDACK demonstrates higher rancorous behavior-detection rates in certain circumstances, while does not greatly affect the network performances.