This document discusses distributed intrusion detection systems for wireless sensor networks. It begins by providing background on wireless sensor networks and the security issues they face, such as denial of service attacks, routing attacks, and Sybil attacks. Traditional intrusion detection systems cannot be directly applied to wireless sensor networks due to their resource constraints. The document then examines the need for intrusion detection systems in wireless sensor networks to provide a second line of defense against attacks. It outlines features an intrusion detection system should have to be suitable for wireless sensor networks, such as being distributed, minimizing resource usage, and not trusting any single node. Finally, it categorizes different types of intrusion detection system architectures for wireless sensor networks, including stand-alone, distributed