By Mick Krever, CNN

The former director of the U.S.’s National Security Agency, General Keith Alexander, warned Thursday that the NSA, mired in controversy over alleged overreach, will inevitably come under another kind of negative scrutiny when the next terrorist attack comes.

“I do think an attack is going to come and hit us or Europe,” he told CNN’s Christiane Amanpour in an exclusive interview. “And then people are going to swing this right around.”

“What is it that NSA actually does? Let’s get those facts on the table.”

“Put it on the table, look at it, and say is that a reasonable way to do it? And if not, what would you suggest? What would others suggest? Nobody’s been able to come up with a better fix.”

Thursday marks one year since the first revelations from leaker Edward Snowden were revealed. General Alexander led the spying organization until earlier this year, and has since founded a cybersecurity company, Ironnet.

“We do need a debate: Where should the line be on civil liberties, privacy, security? And I don't think there's a line; there's a balance. How do we do both?”

Amanpour asked Alexander, “Do you get that the trust has been broken?”

“Yes,” he said. “To be completely candid on this, part of it is we haven't defended ourselves well publicly. You know, we got way behind in the media on this in part because we were concerned that we'd reveal things that would hurt our nation.”

“As a consequence, the media took off with a lot of facts or information that wasn't factually correct.”

Whether it is just a public relations problem, as Alexander says, or whether there are genuine issues with the way the NSA gathers information has been the subject of much global debate.

Germany’s chief federal prosecutor announced on Wednesday that he had opened a criminal investigation into NSA spying on Chancellor Angela Merkel’s mobile phone.

Alexander said he hoped the probe would not harm the countries’ intelligence relationship, which since Snowden’s revelations has already been quite tumultuous.

“I think that cooperation is absolutely vital, especially for Germany, because the United States provides so much intelligence, especially on the terrorism front, to protect Germany and our other European allies.”

Does the U.S. not, Amanpour asked, also get important intelligence from Europe?

“It goes both ways; but I think on the terrorism front, I think that’s where they really look to the United States for help.”

“I think what we have to do is reset what’s going on in all this area.”

But lest someone think that means doing away with the NSA’s controversial programs, Alexander gave a full-throated endorsement of his former agency’s activities.

“I'm not talking about taking the programs off the table. I think what we've done a terrible job in, is explaining what those programs do.”

“It's legal, it's what they're authorized, and it's effective.”

“There are a series of programs; each of those help us build the picture. And if you start taking some of those off the table, the question is, when does it become too difficult for the analysts to conclude what happened? That's how 9/11 occurred.”