The thing we've learned from the last 20 years of counterterrorism is the significant value you get from removing leadership from the battlefield in degrading the organization.

Do I believe Edward Snowden contributed to the rise of ISIS? Yes. Would they have gotten there without the help he provided them? Probably. Would they have been able to conduct this attack in Paris without him? Maybe. So the honest answer is I don't know.

I'm concerned, too, about ISIS' ability, right, to infiltrate people. But we have got some very effective, robust processes for vetting people. We brought in thousands of Iraqi refugees after the Iraq War. Not a single one has ever turned out to be a terrorist because the vetting was so good.

[Vladimir Putin] complimented him. That led Donald Trump to then compliment Vladimir Putin and to defend Vladimir Putin's actions in a number of places around the world.

What I want you to know is that 'Zero Dark Thirty' is a dramatization, not a realistic portrayal of the facts.

ISIS went to school on how we were collecting intelligence on terrorist organizations by using telecommunications technologies. And when they learned that from the [Edward] Snowden disclosures, they were able to adapt to it and essentially go silent.

Companies made these decisions about encryption when they were finding it very difficult to sell their products overseas because the [Edward] Snowden disclosures created the impression that the U.S. government was inside this hardware and software produced by them. They needed to do something to deal with the perception.