The US Defense Department lost 24,000 files to \"foreign intruders\" in March in what appears to be one of the most damaging cyberattacks to date on the U.S. military, the Washington Post quoted a top Pentagon official as saying. US Deputy Defense Secretary William J. Lynn III stated in a speech about the Pentagon\'s cyber strategy that the unspecified data had been stolen from a defense contractor. He did not say who was believed to be behind the attack or describe the nature of the files that were stolen.