As he retires and heads into the private sector, Shawn Henry looks back at the growth in the cyber crime problem.

The FBI's top cyber cop retires today after nearly a quarter century in federal law enforcement.

Shawn Henry started looking into computer issues in the run up to Y2K (the arrival of the year 2000). He says that experience left him hungry to learn more about the way electronics were changing the way we live — and the way criminals operate.The movement of so much sensitive information online poses an "existential threat," according to Henry.

"I think about the threat to our critical infrastructure and the ability for somebody to reach out from around the globe and to critically impact some of our most important capabilities as a nation," Henry says. "To touch the electric power grid, to touch the water or the sewer or the transportation system, and how dangerous that is for us and how relatively easy I think it can be."

Henry says he worries not just about intrusions by people working on behalf of foreign governments, but also the influence of organized crime groups and loose networks such as Anonymous and Lulz Sec who may not even know each others' identities.

"The average American doesn't realize how significant this threat is. I think when we tell people that there's a bomb that's going to go off, that resonates with people ... because they can see the carnage; they've seen it on TV or on the movies and they know what that means," he says. "But when you talk about somebody coming into your network, exfiltrating all your data, stealing your personally identifiable information, the data's still there, which means for most people, you can still see it, [so] it's not real to them."

In recent months, high level Obama administration officials have tried to sound a cyber alarm. FBI Director Robert Mueller told Congress the threat would soon surpass terrorism as the bureau's top priority. Defense Secretary Leon Panetta worried aloud about a cyber attack that "could be the equivalent of Pearl Harbor." And Director of National Intelligence James Clapper said new technologies were outpacing the government's ability to keep up.

Henry says the FBI has worked to hire people with technology expertise and to place those trained agents inside 63 different countries, forming partnerships with law enforcement in Eastern Europe and working side by side to bring hackers to justice.

His introduction to federal government came as a file clerk in 1983, but his first post as an FBI agent was in Washington, D.C. in the late 1980s. A couple decades later, Henry came "full circle" and was appointed to lead the FBI's Washington field office, one of the bureau's largest.

Henry says the current response to the cyber threat is "not sustainable." It leaves too many secrets exposed, he says, and people and companies need to do more to protect themselves from cyber thieves. As he told a conference, "computer security has become an endless game of defense, which is both costly and unsurvivable in the long term."

He says he will keep working on cyber security issues when he leaves the FBI for an unspecified job in the private sector in the Washington area. [Copyright 2012 National Public Radio]