The notorious Operation Shady RAT, the lately uncovered multiple-year-long cyber attacks series discovered by McAfee, possibly comes from China.

See the below excerpt from Wikipedia as of August 9, 2011:

The report suggests that the targeting of various athletic oversight organizations around the time of the 2008 Summer Olympics "potentially pointed a finger at a state actor behind the intrusions". That state actor is widely assumed to be the People's Republic of China. 

http://en.wikipedia.org/wiki/Operation_Shady_RAT