Prosecutors called Chi Mak the "perfect sleeper agent," though he hardly looked the part.
For two decades, the bespectacled Chinese-born engineer lived quietly with his wife in a Los Angeles suburb, buying a house and holding a steady job with a U.S. defense contractor, which rewarded him with promotions and a security clearance.
Mak was sentenced last week to 24 1/2 years in prison by a federal judge who described the lengthy term as a warning to China not to "send agents here to steal America's military secrets."
But it may already be too late: According to U.S. intelligence and Justice Department officials, the Mak case represents only a small facet of an intelligence-gathering operation that has long been in place and is growing in size and sophistication.
The Chinese government, in an enterprise that one senior official likened to an "intellectual vacuum cleaner," has deployed a diverse network of professional spies, students, scientists and others to systematically collect U.S. know-how, the officials said.
Some are trained in modern electronic techniques for snooping on wireless computer transactions.
Others, such as Mak, are technical experts who have been in place for years and have blended into their communities.