A process identifier transition monitor captures and assesses activities associated with a microprocessor or a microcontroller. Monitoring and assessment is performed by detection of process identifier transitions, which may be driven by an occurrence of one or more activities, such as execution of application software, system hardware mechanisms, or processor-internal mechanisms. Process identifier transitions are assessed to determine whether such transitions were expected. If a detected process identifier transition was not expected, then a system alert may be transmitted or some other appropriate response taken within the system.