FRONTLINE producer Michael Kirk dropped by Boston Public Radio on Tuesday to chat with Jim Braude and Margery Eagan about a fascinating new documentary that chronicles the rise of NSA's secret surveillance program and the employees who stood up to it. Watch the first of FRONTLINE's two-part documentary The United States of Secrets here. Part two premiers on May 20.

Margery Eagan: What's this documentary about?

Michael Kirk: There was an agency in the United States of America that had spied on and got its fingers slapped for doing it in the 1970s. The great bright white line at the agency, which was unbelievably powerful in its ability to surviel, eavesdrop, and wiretap, was never turn those eyes and ears towards Americans. And the people who worked there believed it. And then, this thing called 9/11 happened and (…) faster than you could imagine, the rules were changed. The lines were blurred, and the government, the National Security Agency, turned all of that power on the American people, and the people who did the turning, the scientists (…) witnessed it and many many of them worried about it, and talked to us.

ME: NSA engineer Edward Loomis spoke about how deeply he regrets the inaction of the NSA, and a middle ground where there might have been something between having no idea and finding out about this on television and where we eventually went. Was he correct about that? Was there a middle ground?

MK: Yes.  The Cold War was over. We weren't interested in spending lots of money on spy things around the world. We didn't yet know that there was a threat coming from a group called Al Qaeda. But the guys [at the NSA] watching Silicon Valley grow, said "Hey wait a minute, we're behind the curve here," and they went to work on a program called Thin Thread, which was very straight forward. Essentially, what it would do was kind of grab people in this big drag network set up, kind of like Facebook. Encrypt the ones that were in America, because they knew many of the Internet hubs are running through the United States, but the law seemed to preclude them from knowing about Americans. So, they encrypted the data, anonymizing the American portions of it, unless they heard something.

"As they say, it's never the crime, it's always the cover up."

[For example] a safe house in Yemen calling a house in San Diego. Then they could go the FISA Court, a secret court in the Justice Department, and say to them, 'We need a warrant so we can listen, and explore how many phone calls were from Yemen to this number, and who from this number in San Diego, where else did they call in the United States? And we can find people.'

In three steps we can create several million people who are connected to a phone call from Yemen. And they knew that they could do that, but they had to create a thing a system that was relatively inexpensive, very elegant in its ability to capture lots of people, and anonymizing Americans so they could do it in the United States. They thought they had it, but the NSA, nervous at the time about crossing that line into American spying, wouldn't let them go.

ME: One of the encouraging things was the bravery of some of the people who knew something was wrong and tried to do something about it...tell us about some of these people.

MK: We call them the Thin Thread group. The guy who started it-- a crypto mathematician named Bill Binney, there's a guy named Kirk Weepy, there's Ed Loomis who we've already heard, they were all working inside the organization following the rules. These are rule followers- 40 years in the government, former military, a lot of them trying to get the inside bureaucracy of the NSA to pay attention and not do what they considered to be illegal activity.

The NSA bosses wouldn't listen to them, they then took it to a woman named Diane Rourke, who is this amazing figure-- a Senate staffer who's in the House Intelligence Committee. She's just a spectacularly powerful force that said wait a minute, and did everything inside the government-- not going to the press, not breaking any of the rules-- inside the government to get it changed.

But of course the importance of the secret was so critical to the existence of it. I mean, in many ways that's what the film is about. It's about what kind of secrets we'll try to keep. As they say, it's never the crime, it's always the cover up. And in this case, it was the idea that it didn't even exist, and that had to be the way they all played it, well Diane and the Thing Thread Group were trying to break it. (…) Those people, in the face of that kind of force (...) is the most courageous thing that anybody's done in the government in a long long time.

Listen to the full interview with FRONTLINE producer Michael Kirk above. Watch a pre-view of the documentary here.