The Chinese have always denied this, although their cyber fingerprints do tend to get left on everything. Apparently Obama will discuss cybersecurity with Chinese President Xi Jinping when the two leaders meet in California next week. He will have something topical to talk about. There was a Washington Post report that Chinese hackers had gained access to designs of more than two dozen major US weapons systems.
Cyber issues were a key concern for the United States and raised at every level of meetings between US and Chinese counterparts, the White House said. Of course Obama’s hands are tied on the issue. If he hacks off the Chinese too much they will just cut off manufacturing to the US for a couple of weeks and the Civilisation will collapse.