The invention is directed to systems and methods for detecting the loss, theft or unauthorized use of a device and/or altering the functionality of the device in response. In one embodiment, a device monitors its use, its local environment, and/or its operating context to determine that the device is no longer within the control of an authorized user. The device may receive communications or generate an internal signal altering its functionality, such as instructing the device to enter a restricted use mode, a surveillance mode, to provide instructions to return the device and/or to prevent unauthorized use or unauthorized access to data. Additional embodiments also address methods and systems for gathering forensic data regarding an unauthorized user to assist in locating the unauthorized user and/or the device.