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. Colleagues remembered him as a hard worker who often took paperwork home at night.
Eventually, Mak's job gave him access to sensitive plans for Navy ships, submarines and weapons. These he secretly copied and sent via courier to China -- fulfilling a mission that U.S. officials say he had been planning since the 1970s.
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.