A Radio Frequency based security system for providing security for wireless Local Area Networks (WLAN) that allows the creation and maintenance of arbitrarily shaped secure wireless access areas with boundaries around said wireless Local Area Network and prevents access to the said wireless LAN from outside the perimeter of the secure area. The system includes a plurality of perimeter Radio Frequency Sentry Devices (RFSDs) that are employed to establish the boundaries of said secure area around said wireless LAN. The wireless LAN being secured may be an industry standard IEEE 802.11a, 801.11b or 802.11g based wireless LAN or any other wireless LAN that uses packet based communication protocols. The said RFSDs may be stand-alone devices or they may be connected to a wired or wireless Local Area Network.