If you build - if you spend billions of taxpayer dollars to build a wall over, let's say, a mountain, if you build a 10-foot wall over a 10,000-foot mountain, and someone is determined to climb the 10,000-foot mountain, they're not going to be deterred by the 10-foot wall. It's a matter of common sense.

I hope that the states are taking seriously their obligations to harden the cybersecurity around the election infrastructure that Americans rely upon and need.

I'll never forget what a Catholic priest told me; he said, "If you try to padlock the door, you have to give people an alternative path - an alternative, safer path. You can't padlock, and you shouldn't padlock a burning building."

If you build - if you spend billions of taxpayer dollars to build a wall over, let's say, a mountain, if you build a 10-foot wall over a 10,000-foot mountain, and someone is determined to climb the 10,000-foot mountain, they're not going to be deterred by the 10-foot wall. It's a matter of common sense.

I think that the potential for homegrown terrorist attacks is something that we have to be very concerned about, because, in many respects, it's harder to detect when you have an independent actor who may be living in our midst, in our own communities.

There's a lot of sensitivity about federal involvement in elections around the country. I think that it would be appropriate to consider - whether there should be some basic federal minimum standards to the cybersecurity around the election infrastructure. We have federal standards for aviation security, for auto safety, for a lot of things, and elections are pretty important in the country.

The good news is that the international coalition, in which our military contributes, has done a lot to reduce the ground space, the territory in Iraq, Syria that ISIL once occupied a couple years ago. That's a good thing. And a lot of that, frankly, has occurred in Trump administration, so I'll give them credit for that.