This isn't meant to exhibit a personal paranoia, but is it reasonable to keep the prospect of terrorism more in scope if we allow for hacking efforts that would exploit security vulnerabilities in existing systems? Gut feel (no basis, though) is that it may be more likely to take that approach than the steal-materials-and-build-and-launch one.

All it takes is a coup of a nuclear-armed nation, and the barrier to entry on that project keeps dropping as states with a recent history of fanatic-deposes-weaker-fanatic coups join the club.