Except if you have a computer with Intel Management Engine or the AMD equivalent. Then it can be accessed when off. And mobile devices can be turned on remote

Except if you have a computer with Intel Management Engine or the AMD equivalent. Then it can be accessed when off. And mobile devices can be turned on remotely as well. You'd have to pull the plug or remove the battery to be truly off but nobody goes through that hassle. While currently it would take a state actor to do this eventually this will trickle down into to the hackers.