The document presents Enhanced Adaptive Acknowledgement (EAACK), a secure intrusion detection system for mobile ad hoc networks (MANETs). It discusses common attacks on MANETs like denial of service and eavesdropping. Existing intrusion detection systems for MANETs like Watchdog, TWOACK and AACK are summarized along with their limitations. EAACK is proposed to address these limitations through local and global integration of intrusion results, using home agents to gather system information, and a classifier to identify attacks. EAACK consists of acknowledgements, secure acknowledgements and misbehavior report authentication to detect malicious nodes. It is concluded that detection is important to manage secure networks in addition to prevention mechanisms.