One cable, dated early this year, quoted a Chinese person with family connections to the elite as saying that Mr. Li himself directed an attack on Google’s servers in the United States, though that claim has been called into question. In an interview with The New York Times, the person cited in the cable said that Mr. Li personally oversaw a campaign against Google’s operations in China but the person did not know who directed the hacking attack…

That confidence may also reflect what the cables show are repeated and often successful hacking attacks from China on the United States government, private enterprises and Western allies that began by 2002, several years before such intrusions were widely reported in the United States.

At least one previously unreported attack in 2008, code-named Byzantine Candor by American investigators, yielded more than 50 megabytes of e-mail messages and a complete list of user names and passwords from an American government agency, a Nov. 3, 2008, cable revealed for the first time.

Precisely how these hacking attacks are coordinated is not clear. Many appear to rely on Chinese freelancers and an irregular army of “patriotic hackers” who operate with the support of civilian or military authorities, but not directly under their day-to-day control, the cables and interviews suggest.