Earlier quoted context omitted.
Took me a while to figure out the overheat thing. There's a character skill that highlights who's hacking you, which you should get. Then once you know who's hacking you, you either need to shoot them, or disable the camera (by hacking or shoot) they're using to hack you with (they can use cameras to scan, just like you can).
I have that skill and have yet to see it highlight anyone. I have a feeling its just another bug where the ai can see you through walls.
The skill gives you a yellow damage indicator and highlights the hacker in yellow outline.