Intel x86 CPU's hide another tiny CPU. These will eventually lead to virtually undetectable rootkit attacks. https://boingboing.net/2016/06/15/intel-x86-processors-ship-with.html
This is not particularly new. The Baseboard Management Controller has had a similar capability for ages, with less security. This has been mitigated to some extent by the fact that everyone KNOWS if there is a BMC because they actually ORDER it; it's usually only installed on servers and other enterprise hardware. The Intel implementation of the IME appears (so far) to be fairly secure, although it is obviously only a matter of time before someone figures out a way to compromise it. Since a fair bit of it is baked into the silicon, it will probably require someone to actually decap a chip to see what's going on. Unfortunately, that also means that once it is compromised, it likely can't be fixed, since what little we know indicates it's on ROM, not EPROM or FLASH.
As always, you know a lot more about the science and arts of all things computer related than your humble correspondent. I don't know how anyone can keep such a heavy load of knowledge inside their brain. Can processors really be "decapitated," would this be accomplished by shaving one ten thousandth of an inch off of the top at a time?
I've not actually tried it myself, but my understanding is essentially what you've described; slowly shave the top of the package until you get to the silicon. Once you've done that, then start looking things over with a microscope.
Chips and especially CPU's are extremely interesting when magnified. AMD used to do this with their new processors, in aid of advertising them more effectively. Maybe Big Blue 2 did too?
