This paper describes the security threats associated with 802.11 based wireless local area networks (WLANs) and outlines a comprehensive architecture for a wireless intrusion protection system (WIPS). The AirDefense WIPS based on this architecture is currently used to monitor and protect tens of thousands of networks and over one million devices around the globe in almost 500 enterprises, healthcare organizations and government agencies. The paper also describes the essential attributes that define the figure of merit (FOM) of a WIPS. The FOM can be used to quantify and compare the performance and functionality of a WIPS and distinguish enterprise class solutions from simple checkbox systems.