The Chinese government approaches its spycraft differently from either Russia or the United States. It is often much more patient. The Chinese may take years to develop a source and plant one inside American intelligence organizations. But they have managed to do just that inside the F.B.I., the C.I.A., the Pentagon and the State Department.

Some analysts attribute Beijing’s successes to an American lack of understanding of China’s approach. Paul Moore, a former China analyst for the F.B.I., explains the difference this way:

“If a beach were a target, the Russians would send in a sub, frogmen would steal ashore in the dark of night and collect several buckets of sand and take them back to Moscow. The U.S. would send over satellites and produce reams of data. The Chinese would send in a thousand tourists, each assigned to collect a single grain of sand. When they returned, they would be asked to shake out their towels. And they would end up knowing more about the sand than anyone else.”

In other words, the Chinese have infinite patience. A real-life example is China’s attempt to plant a man named Glenn Shriver as a mole in the C.I.A. Mr. Shriver grew up in a Michigan suburb, learned Mandarin in college and, while a student in Shanghai in 2004, answered an ad inviting an essay on United States-China relations. A woman who called herself Amanda paid him a small fee and later introduced him to a “Mr. Wu” and “Mr. Tang.” All three were agents of China’s Ministry of State Security.

They asked him to apply for a State Department job. He flunked the Foreign Service examination twice but was paid $30,000 for trying. He was then paid $40,000 more to apply to the C.I.A.’s clandestine service. By then, the Americans were on to him. Lured back to America in 2010 for what he thought was a final screening, he was arrested, convicted and sentenced to four years in prison after accepting a plea deal.

China’s most startling and disturbing coup in penetrating American intelligence agencies occurred after the F.B.I. recruited Katrina Leung, a prominent Chinese-American in Los Angeles, because she was known to have extensive contacts in the Chinese government. But later, it turned out, she had affairs with two top F.B.I. counterintelligence agents in California, James J. Smith and William Cleveland Jr., and became a double agent for some 18 years, starting in 1984.