In a device having a plurality of circuits that can store at least a first value and a second value, a method can include configuring at least one circuit to persistently store the first value; determining whether the at least one circuit is storing the second value; and initiating a countermeasure if the at least one circuit is storing the second value. Determining whether the at least one circuit is storing the second value can include detecting whether the device has been attacked. Non-limiting examples of initiating a countermeasure can include resetting a portion of the device, powering down a portion of the device, activating an alarm circuit, causing protected data stored in the device to be erased, causing portions of the device to self-destruct, or causing the device to not respond to input applied to the interface.