Methods and systems for protecting the computer network against unauthorized access are disclosed. Information is reported about each network device connected to the network and/or one or more corresponding users. The reported information is correlated to determine if any unauthorized devices are connected to the network. To report the desired information, each device authorized to use the network may be provided with an agent configured to report information about the device to which it corresponds and information about one or more neighboring devices. A "reporting your neighbor" method may be used wherein each network device report its address and the address of its neighbors may be used to determine if any device is not reporting its address. Alternatively, each agent may report information about its device's physical location, e.g., by global positioning satellite (GPS). A door badge system may be used to provide user location information.