Chinese hackers have for years targeted the United States military to steal information and the Pentagon says they have previously swiped crucial data on the new F-35 stealth fighter, the advanced Patriot PAC-3 missile system and other highly sensitive projects.
The data was reportedly stolen from a Navy contractor who works for the Naval Undersea Warfare Center in Newport, Rhode Island, although the Post's sources would not say which contractor was targeted.
It said the stolen information amounted to 614 gigabytes of material, including secret plans to develop a supersonic anti-ship missile for use on US submarines by 2020.
The Post said the hacking took place in January and February, according to USA officials speaking on the condition of anonymity.
A commander of the US Navy, Bill Speaks, said that measures were in place requiring companies to notify the government when a "cyber incident" had occurred on networks that contained "controlled unclassified information".
Former Sen. Jim Talent (R-Mo.), who is a member of the U.S. China Economic and Security Review Commission, called the incident 'very disturbing, ' adding however that reports of the Chinese hacking scheme was nothing new.
The newspaper said it had agreed to withhold some details about the compromised missile project after the Navy said their release could harm national security. "It would be inappropriate to discuss further details at this time".
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"The breach is part of China's long-running effort to blunt the U.S. advantage in military technology and become the preeminent power in East Asia".
It also comes as President Donald Trump continues to court Beijing in his efforts to denuclearize North Korea.
The Chinese hackers breached the contractor's systems in January and February and made off with 614GB of data on signals, sensor data, cryptographic info, the Navy's electronic warfare library and material on a project known as Sea Dragon. Sea Dragon is a $300 million project scheduled for underwater testing in September.
China has recently made it a priority to increase its development of undersea warfare to diminish the gap in the US superiority in this area.
While the information was stored on the contractor's unclassified network, it was described as "highly sensitive" in the Post report.
The investigation into the breach, which is being jointly conducted by the Navy and the FBI, is now underway, The Post reported.