The Pentagon on Thursday revealed that in the spring it suffered one of its largest losses ever of sensitive data in a cyber attack by a foreign government. It's a dramatic example of why the military is pursuing a new strategy emphasizing deeper defenses of its computer networks, collaboration with private industry and new steps to stop "malicious insiders." William Lynn, the deputy secretary of defense, said in a speech outlining the 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.