If an adversary didn't target our power plants but they did target the core routers, the backbones that tie our internet connections together, entire parts of the United States could be cut off. That would have a tremendous impact on us as a society and it would have a policy backlash.

How do we preserve our civil rights, our traditions as a liberal democracy, in a time when government power is expanding and is more and more difficult to check?

We should never allow computers to make inherently governmental decisions in terms of the application of military force, even if that's happening on the internet.

A zero-day exploit is a method of hacking a system. It's sort of a vulnerability that has an exploit written for it, sort of a key and a lock that go together to a given software package. It could be an internet web server. It could be Microsoft Office. It could be Adobe Reader or it could be Facebook.

Some months after [Keith Alexander] made that statement [Edward Snowden cause grave and irrevocable harm to the nation], the new director of the NSA, Michael Rogers, said that, in fact, he doesn't see the sky falling. It's not so serious after all.

We have to decide why terrorism is a new threat. There has always been terrorism.

I'm not a communist, a socialist or a radical. But these issues have to be addressed.