DAVID GREENE, HOST:
Robert Mueller arrived as director of the FBI in 2001, a week before Sept. 11th. That attack on the United States changed the job. He had to try to remake the FBI into an agency capable of anticipating terrorist strikes and cyberattacks before they happen.
Mueller has mostly avoided the limelight. His friend, former CIA Director George Tenet, says he's a different type.
GEORGE TENET: St. Paul's, Princeton, a high Protestant with a locked jaw, blue blazer, tacky khaki pants, penny loafers, maybe a little Vitalis and Old Spice to boot.
GREENE: Mueller is about to end his tenure as FBI director. On the eve of his departure, he sat down with NPR's Carrie Johnson to talk about his service and the challenges for his successor.
CARRIE JOHNSON, BYLINE: With his 12 years at the FBI drawing to a close, the decorated former Marine opened up a bit about what leading the bureau has been like in an age of al-Qaida and more. The surprises came almost from day one.
DIRECTOR ROBERT MUELLER: I had been a prosecutor before, so I anticipated spending time on public corruption cases and narcotics cases and bank robberies, and the like. And Sept. 11th changed all of that.
JOHNSON: Robert Mueller says it took him a while to realize how drastically the mission of the FBI had to change. Conversations with President George W. Bush and again, with President Obama, focused his mind on this thought.
MUELLER: What is the FBI doing to prevent the next terrorist attack?
JOHNSON: To try to answer that question, Mueller moved 2,000 agents from gumshoe criminal investigations into counterterrorism and national security. And in a huge shift in mindset, he also set up an intelligence operation within the bureau, to analyze threats. That transformed an organization filled with men in dark suits. One of them was Mueller's former deputy and right-hand man, John Pistole.
JOHN PISTOLE: He directed and implemented what is arguably the most significant change in the FBI's 105-year history.
JOHNSON: But as Mueller prepares to exit the stage, lawmakers are asking whether the bureau has changed its stripes in all the ways that count. A big one involves sharing information with counterparts. A few months ago, Boston police criticized the FBI for not telling them about its scrutiny of one of the marathon bombers before pressure-cooker bombs exploded at the race site. Texas Republican Michael McCaul, head of the House Homeland Security Committee, put it this way at a recent hearing.
REP. MICHAEL MCCAUL: We learned over a decade ago the danger in failing to connect the dots. My fear is that the Boston bombers may have succeeded because our system failed. We can, and we must, do better.
JOHNSON: Mueller says the FBI is light years ahead of where it was on information-sharing, and that he fosters a close relationship with federal agencies and local police. But in recent years, his job protecting national security changed again. The accused Boston bombers and the Army psychiatrist who carried out a massacre at Fort Hood, Texas, to support the Taliban represent the new face of terrorism, Mueller says.
MUELLER: You have individuals who are not aligned with any particularized group, who can be radicalized and find a weapon of choice and then kill American, innocent civilians. And unfortunately, we have to be prepared for that. It's much more difficult to discern, but we could anticipate that there may be more in the future.
JOHNSON: For nearly a dozen years now, Mueller has started his morning - every morning - with a secret threat briefing. So I wondered...
What did keep you up at night the most? What were the hardest moments for you?
MUELLER: Well, the thing I worry about most is the possibility of a bomb on an airplane, here, in this day and age.
JOHNSON: That's a surprisingly specific answer, and one with roots in recent history. In 2009, a Nigerian student with links to al-Qaida in Yemen tried to take down a plane over Detroit on Christmas Day. The man who made those bombs, Mueller says, is still on the loose.
That airliner incident was personal for Mueller. As a prosecutor, he worked for years on the investigation of the bombing of Pan Am 103 over Lockerbie, Scotland, in 1988.
MUELLER: And people who are looking at, for instance, our intelligence programs and criticizing them, I would say: Spend a few moments with families of those who have lost their loved ones, whether it be Pan Am 103 or Sept. 11th alike; and it puts it in a wee bit different context.
JOHNSON: About those critics - new revelations about surveillance of email and phone calls within the U.S. by the National Security Agency and the FBI have prompted bipartisan calls in Congress to restrict the federal government's ability to snoop on its own citizens. The White House has launched a widescale review.
Mueller says the FBI's close ties to the Justice Department guide what agents do, and impose checks and balances on their actions. And when investigators uncovered problems with agents' use of national security powers, Mueller says he did his best to solve them. Former Inspector General Glenn Fine, who frequently held Mueller's feet to the fire, says it was a successful run for the director.
GLENN FINE: The measure of a tenure and the measure of a leader, is whether when he learns of those problems, he fixes them. And I think that's what he did. He did it in a tireless fashion and that's - he deserves credit for that.
JOHNSON: Lately, Mueller's been focusing his energy on a new area of work for the FBI: cyberattacks on banks or utilities. And in another pivot point for his agency, Mueller worries the cyberthreat will soon overtake al-Qaida as the bureau's biggest priority.
MUELLER: Before we have a substantial incident, which would serve as a wake-up call, we need to do everything we can to prevent that happening.
JOHNSON: No small challenge for a bureau that's fought for years to bring agents into the digital age, spending nearly half a billion dollars on a troubled internal computer system - an effort Mueller says is now on track.
Over the last few months, something else has been on the mind of the FBI director, a problem he's leaving for his successor - the budget crisis. Mueller says there's only so much the bureau can cut back on cars and travel and IT upgrades. So priorities for agents in the field will have to give.
MUELLER: I expect the special agent in charge to make certain that there is no Mohammed Atta, a terrorist, swimming in the waters in that division. And so what's going to be hit is white-collar crime; what's going to be hit is violent crime - we're not going to be able to do as much as we'd want there; organized crime.
JOHNSON: Starting next week, Mueller is inviting his successor, Jim Comey, to shadow him for the daily threat briefing and other tasks until Mueller says goodbye to the bureau Sept. 4th. After that, the former Marine says he'll write and teach, and do a little investigative work of his own.
Justice Department colleague David Margolis recently suggested at an awards ceremony that his old friend Mueller would be perfect for another role.
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DAVID MARGOLIS: A job he was born for, and has spent his whole life preparing for - drill instructor at Parris Island.
JOHNSON: Even the taciturn Robert Mueller broke into a huge laugh at that one.
Carrie Johnson, NPR News, Washington.
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