Should we be worried about a cyber war?

A few weeks after Barack Obama's election, the Chinese began flooding a group of communications links known to be monitored by the N.S.A. with a barrage of intercepts, two Bush Administration national-security officials and the former senior intelligence official told me. The intercepts included details of planned American naval movements. The Chinese were apparently showing the U.S. their hand. ("The N.S.A. would ask, 'Can the Chinese be that good?' " the former official told me. "My response was that they only invented gunpowder in the tenth century and built the bomb in 1965. I'd say, 'Can you read Chinese?' We don't even know the Chinese pictograph for 'Happy hour.' ")

Why would the Chinese reveal that they had access to American communications? One of the Bush national-security officials told me that some of the aides then working for Vice-President Dick Cheney believed -- or wanted to believe -- that the barrage was meant as a welcome to President Obama. It is also possible that the Chinese simply made a mistake, given the difficulty of operating surgically in the cyber world.