Even computers need a tinfoil hat!  

If this is indeed possible, I don't think it would work on a massive scale, and I also don't think it would work for every possible environmental case. Sure, somewhere without much metal and without much background EM waves would be ideal, but you're not going to get that for anything but a small number of situations IRL. It defies common sense that a busy city environment would be an easy place to target a computer in this way, and if there was another agent trying to do the same to another target a couple doors down, you'd probably have to work in shifts. NSA can't bend the laws of physics in the same way they bend the law of the land. Unless we're actually in The Matrix.