Abstract: A method and apparatus is provided for monitoring performance of an processor to detect tampering and place the processor in a safe operating state that prevents unauthorized access to contents of the processor. In one example, the method and apparatus compares a measured value of an operating parameter (i.e., a temperature, supply voltage or clock signal) to predefined limits to identify an out of limits measured value. If an out of limits measured value is detected during a normal operating mode, the processor enters a reset mode, and if an out of limits measured value is detected during power up or reset, the processor in retained a reset mode.