Some implementations of the present invention provide methods and devices for detecting the theft of, and disabling, electronic devices such as computers and network devices. The devices may be disabled when a signal is not detected, e.g., for a predetermined period of time. For example, a radio frequency (“RF”) signal (e.g., a beacon), an Internet Protocol (“IP”) signal or the like may define a space within which the devices may be operated with complete functionality. Outside this space, the devices will be disabled, at least to some degree. The degree of disablement may depend on the length of time since the signal was last detected. Alternatively, the devices may be disabled when a signal is detected: some such implementations define “portals,” “choke points” or the like past which a device may not be transported without some degree of disablement.