China allegedly exfiltrated classified information pertaining to US Navy projects after a successful cyber-attack on an unspecified Navy contractor resulted in the loss 614 gigabytes of sensor data, cryptographic information, submarine electronic warfare, and the exposure of a classified project known as Sea Dragon.

The contractor, believed to work for the Naval Undersea Warfare Center, allegedly stored the sensitive information on an unclassified network. The Sea Dragon project seems to be a Pentagon initiative aimed at bringing “disruptive offensive capability” by “integrating an existing weapon system with an existing Navy platform.”

The trove of data allegedly also includes information about a supersonic anti-ship missile that’s supposed to be fitted onto US submarines by 2020, increasing the strategic military value of the theft. Officials have estimated that the Chinese government is behind the attack, as this type of military intelligence is exactly what China needs to bridge the technology gap between its navy and the United States’ navy.

“So anything that degrades our comparative advantage in undersea warfare is of extreme significance if we ever had to execute our war plans for dealing with China,” said James Stavridis, dean of the Fletcher School of Law and Diplomacy at Tufts University and a retired admiral who served as supreme allied commander at NATO.

While this is not the first time the US has blamed China for breaches on government contractors that resulted in the loss of sensitive military research and information, this incident has been attributed to the Chinese Ministry of State Security, a civilian agency tasked with counterintelligence.

“We treat the broader issue of cyber-intrusion against our contractors very seriously,” said Cmdr. Bill Speaks, a Navy spokesman. “If such an intrusion were to occur, the appropriate parties would be looking at the specific incident, taking measures to protect current information, and mitigating the impacts that might result from any information that might have been compromised.”