Hack through Power source
brk: In the sense of "take control", not really.In the sense of "monitor various actions/activities", then yes (at least in theory).There have been some studies and experiments where you can determine what a CPU is doing or executing by monitoring very finite changes in the current draw of the power supply.  To do this with any accuracy, you would have to install a rather precise power monitoring device on the circuit powering the PC itself, and most likely on the power cord going directly to the PC (so as not to pick up electrical data from other devices on the same circuit).You would also more than likely need brief physical access to the PC itself, so that you could calibrate to various CPU states.So, it is somewhat possible, but not in any practical application.