It's the 'Holy Grail' of exploitation though - if you can back-door the hardware as she's suggested in the paper, nothing in the software stack can detect it, which means you cannot know if your machine is secure or not.
The fact it's very hard to achieve means it's not something that's likely, but if a government decides that it wants to commandeer your computing hardware, there's nothing you could do to stop them, plus you'd never know that it occurred.