Needless to say, this tweet prompted a number of subtle (and not so subtle) responses; it is just vague enough to not be 100% sure he is actually joking (because the software verification problem is trivial, right?).
Did North Korea hack Sony? I doubt it; perhaps it was from an unexpected agent.
N.B. high-profile physicists appear to be quite happy to make bold statements to the media on issues outside of their areas of expertise…