I would be quite impressed if NSA had the ability to write microcode updates themselves. I'd imagine they are not exactly trivial and require intimate knowledge of the actual silicon.
Which is why this guy is feeling around in the dark with bit-errors, because even though there are no secrets on the inside not a single one of intel's 104k employees is willing to throw this guy a bone. Right.
Donning tinfoil hat, NSA is just one part of USG. USG is one of hundreds of countries, zillions of criminal enterprises that would like to get intel's private keys and μcode format.
Given that intel is a large company the odds favor one/more external actors having access.
There's really no way to know without some sort of way for IDS to check μcode. Never going to happen due to the blackbox nature of closed, proprietary systems.
Or we could all just realize that for the time and effort of trying to write a backdoor into a general purpose CPU, which would need huge amounts of memory to be remotely capable of keeping track of code execution and to correctly make an OS remotely exploitable (you know, involving the network stack, probably TCP/IP and other things) rather then just crashing it...that it easier just to email someone an executable saying "I love you.exe" and wait for them to run it.
This is looking through the microscope to determine whether a forest is on fire.
Maybe, it will be one of the harder exploits to code, but very effective to disable certain apps or hide other backdoors. Reprogramming the microcode would be a virus-writer's dream come true, too. Knowing how to do it is probably very hard, as it is probably some RTL.
Intel started releasing reprogrammable microcode after the FDIV bug in the original Pentium made them replace a few hundred thousand CPUs. With programmable microcode, they could replace this operator.
