I uncovered a connection between two of the key players in the Stuxnet drama: Vacon, the Finnish manufacturer of one of two frequency converter drives targeted by this malware; and RealTek, who’s digital certificate was stolen and used to smooth the way for the worm to be loaded onto a Windows host without raising any alarms. A third important piece of the puzzle, which I’ll discuss later in this article, directly connects a Chinese antivirus company which writes their own viruses with the Stuxnet worm.I don't think this is altogether convincing, but it is certainly worth consideration. If you are into Stuxnet, read the whole thing.
...China has an intimate knowledge of Iran’s centerfuges since, according to one source quoted above, they’re of Chinese design.
China has better access than any other country to manufacturing plans for the Vacon frequency converter drive made by Vacon’s Suzhou facility and specifically targeted by the Stuxnet worm (along with an Iranian company’s drive).
China has better access than any other country to RealTek’s digital certificates through it’s Realsil office in Suzhou and, secondarily, to JMicron’s office in Taiwan.
China has direct access to Windows source code, which would explain how a malware team could create 4 key zero day vulnerabilities for Windows when most hackers find it challenging to develop even one.
...As far as China goes, I’ve identified 5 distinct ties to Stuxnet that are unique to China as well as provided a rationale for the attack which fits China’s unique role as Iran’s ally and customer, while opposing Iran’s fuel enrichment plans. There’s still a distinct lack of information on any other facilities that suffered damage, and no good explanations for why there was such massive collateral damage across dozens of countries if only one or two facilities in one nation state were the targets however based solely on the known facts, I consider China to be the most likely candidate for Stuxnet’s origin.