It said a number of people told it that Stuxnet was a joint project between the United States and Israel—but didn’t say if Israel did anything beyond the testing.
A truly joint project would be very unusual. Intelligence agencies often cooperate and coordinate and share information, but actual joint operations are rare in the history of espionage.
While the Times describes Stuxnet as a joint project, it mentions no other role for Israel except as a test center.
The newspaper said the Stuxnet project began in 2008 when Siemens, the German company that sold Iran the core computer system for the Natanz enrichment plant, gave an American government laboratory access to its programs to help it identify weaknesses. That was the Idaho National Laboratory, one of 17 laboratories that are part of the US nuclear research system.
The article does not say whether Stuxnet was developed at that laboratory or somewhere else. In fact, it is totally silent or who and where Stuxnet was developed.