From time to time I hear the fan spin up on my MacBook Pro (2012) with few to no applications running. I check the activity monitor for CPU usage, and see the AntiTheftHelper process taking 90 - 100% of a CPU core.
When I connect an external microphone to the jack, it is not working. I can see it in the "Sound" tab, but the levels is very low. I have tried with several microphones.