Pentagon reveals hackers' theft of sensitive data

The Pentagon has revealed that it suffered one of its largest losses ever of sensitive data in a March cyberattack by a foreign government - a dramatic example of why the military is emphasizing deeper defenses of its computer networks, collaborating with private industry and taking new steps to stop "malicious insiders."

William Lynn, the deputy secretary of defense, said Thursday in a speech outlining the new strategy that 24,000 files containing Pentagon data were stolen from a defense industry computer network in a single intrusion in March. He offered no details about what was taken, but said the Pentagon believes the attacker was a foreign government. He didn't say which nation.

"We have a pretty good idea" who did it, Lynn said in an interview before the speech. He would not elaborate.

Many cyberattacks in the past have been blamed on China or Russia. One of the Pentagon's fears is that eventually a terrorist group, with less at stake than a foreign government, will acquire the ability to not only penetrate U.S. computer networks to steal data but to attack them in ways that damage defenses or even cause deaths.

In his speech at the National Defense University, Lynn said that sophisticated computer capabilities reside almost exclusively in nation-states, and that U.S. military power is a strong deterrent against overtly destructive cyberattacks. Terrorist groups and rogue states, he said, are a different problem and harder to deter.

"If a terrorist group gains disruptive or destructive cybertools, we have to assume they will strike with little hesitation," he said.

The Pentagon has long worried about the vulnerability of its computer systems. The concern has grown as the military becomes more dependent on its own computers and those of its defense contractors, including providers of fuel, electricity and other resources used by the military.

At his Senate confirmation hearing last month, Defense Secretary Leon Panetta cited "a strong likelihood that the next Pearl Harbor" could be a cyberattack that cripples the U.S. power grid and financial and government systems.