Classified military information including missile plans have been stolen from contractors working for the US Navy by hackers linked to China, according to reports.

Contractors working for the US Navy have reportedly suffered a series of breaches in the past 18 months.

Richard Spencer, the secretary of the US Navy, has ordered a review of cybersecurity threats, The Wall Street Journal reported on Friday.

The review follows reports of the theft of classified plans for a supersonic anti-ship missile to be used by submarines. The plans for the missile were found to have been stolen in June during a hacking attack against a contractor for the US Naval Undersea Warfare Center in Rhode Island.

In January and February, hackers stole 64 gigabytes of sensitive data stored on the unnamed defence contractor’s unclassified computer network.

The US government has not definitively linked China to the hacking attacks, but the report said that some malware was shown to have been controlled by a computer in China’s Hainan province. The hackers also used hacking tools which have been used by Chinese-affiliated hacking groups in the past.