New leaks from former National Security Agency (NSA) contractor Edward Snowden show China stole the designs for American-built F-35 Joint Strike Fighter.

In a large top-secret document dump, provided by Snowden to German magazine Der Spiegel, the extent of the ongoing international cyber warfare between the U.S., its allies and the rest of the world has been outlined.

According to Fairfax Media, one of the confidential documents within the latest leak show Chinese spies stole "terabytes" of design and military information relating to the F-35, also known as the Lockheed Martin F-35 Lightning II. The information was used to assist in the design of China's Chengdu J-20 and the Shenyang J-31 stealth fighter jets, as long suspected by the west.

The Chinese J-31, designed off the F-35. Image: Getty Images

The security breach and the retrieval of information regarding the jets is thought to have taken place at the headquarters of Lockheed Martin in 2007.

The information stolen about the F-35 — which is considered the smartest fighter jet in the world — reportedly shows the radar systems, engine schematics and methods for cooling exhaust gases. The jet's standout feature is the ability to strike without being detected by radar.

The cyber espionage by China had previously been reported in 2014 by the Washington Times, but this is the first instance official documents have confirmed the attack.

In October, the Australian government committed A$24 billion to the deployment of 72 of the F-35 jets, making it Australia's largest military purchase, in a move expected to give Australia a regional leg up. The Snowden documents state the Australian government was made aware of the attack.