Re:This can't be a problem (Score 1)

Yes in Linux you can remove the ability to update the microcode. I was only trying to point out that the microcode can be inserted anytime and isn't set in stone at the fab as the GGP suggested.

And a reboot is not required to update microcode, it takes effect immediately.

so, you've got the code (wireshark, tcpdump),

You don't even need that, you can download the code from Intel's site, or see what you have in /etc/firmware/microcode.dat.

the key (embedded in CPU),

As far as I know, nobody has extracted the key.

and the mechanism (kernel support code) - are you implying that this isn't enough to reverse engineer any/or revert microcode changes?

Without that key, the microcode can't be reverse engineered.

But to revert microcode, you simply remove the update mechanism and reboot. Your BIOS maay still hold a microcode update that it applies on boot, though.