Deputy Defense Secretary William Lynn revealed on Thursday that an "unspecified foreign government" was responsible for the theft of 24,000 files this spring from a defense-related computer network.
He made the announcement as the Pentagon publicly released a plan to protect itself against those kinds of computer-based attacks. The Associated Press reported that the DOD has "a good idea" who stole the files, but isn't offering any details.
According to DOD officials, the cybersecurity strategy addresses the "economic, security, law enforcement, military, governance, international development, and internet freedom" aspects of the cyber realm. Because much of the plan is classified, details were somewhat limited.
Joint Chiefs of Staff Chairman Adm. Michael Mullen told This Week In Defense News that he thinks attacks on the nation's computer infrastructure are "the single biggest existential threat that's out there...I think we're going to have to focus a lot more on it."
Attacks in cyberspace may require very little equipment or manpower, can threaten almost any computer system that has a connection to an outside network, and their origins can be very difficult to trace.
Last summer, the Pentagon released its first cybersecurity plan which detailed "five pillars" of strategy: Recognizing that cyberspace is a "new domain of warfare," emphasizing active defenses that look for threats, protecting critical infrastructure like power plants, collaboration and information sharing between agencies, and maintaining a technological advantage.