U.S. Deputy Secretary of Defense William J. Lynn III writes in the latest issue of Foreign Policy about the 2008 hack into a military laptop he calls "the most significant breach of U.S. military computers ever."  Lynn explains the previously classified story: two years ago, a foreign intelligence agent plugged a flash drive into a military laptop and infected a U.S. Central Command network. The military's effort to deal with the worm was dubbed Operation Buckshot Yankee.  This event was a wake-up call; it changed U.S. cyber policy and sparked the creation of the U.S. Cyber Command.
Noah Shachtman of Wired wonders why a foreign spy would go to all the trouble to inject such a harmless worm in the network.