Abstract: A system monitors and detects unauthorized wireless LAN access points and wireless devices. The system includes one or more wireless LAN monitoring devices, which detect and report the presence of unauthorized or “rogue” wireless LAN access points or wireless devices within a predetermined area, for example, within the vicinity of a wired LAN, including indoor and/or outdoor areas. Improved range is achieved through the use of preamplification and sectorized antennas. Larger areas may be covered using additional wireless LAN monitoring devices, which operate independently or cooperate together in the detection process. Geolocation is possible using single or multiple, cooperating monitoring devices. Provision can be made for monitoring devices to provide packet filtering on a wired LAN.