MINIX is actually on a different processor, in Platform Controller Hub. And there are three things you need to know about it:
1. It runs with highest privilege, so it has access to the whole system but you can't access it.
2. Its always running, even when your device is switched off.
3. It has a web server, complete with its own MAC address. There is no discernible way of cutting off its access. (I could be wrong on this one.)
Edit: This is also this open letter[0] from Tanenbaum after he discovered MINIX was being used in Intel ME.
[0]https://www.cs.vu.nl/~ast/intel/
