Independent researchers who monitor Chinese information warfare caution that the Chinese have adopted a highly distributed approach to online espionage, making it almost impossible to prove where an attack originated. “We have to understand that they have a different model for computer network exploit operations,” said James C. Mulvenon, a Chinese military specialist and a director at the Center for Intelligence Research and Analysis in Washington. Rather than tightly compartmentalizing online espionage within agencies as the United States does, he said, the Chinese government often involves volunteer “patriotic hackers” to support its policies.