Intel war

5 things we learned from inside the U.S. intelligence war

In the wake of the attacks in Paris, the world's attention has refocused on terrorism, and in the U.S., conversations about national security have increased in both frequency and force.

The U.S. intelligence apparatus is vast, spanning some 16 agencies, with a staff of more than 100,000 people, a budget above $66 billion and a staggering array of operations, many of which are necessarily secretive.

CNN sought to shed some light on the United States' many intelligence agencies and what they say they are doing to protect the country from threats around the globe. The overview included interviews with some of the nation's top spies, and behind-the-scenes access never before granted to journalists. Here are five things we learned from inside the U.S. intelligence war...