Chinese spies stole key design information about Australia's new Joint Strike Fighter, according to top secret documents disclosed by former US intelligence contractor Edward Snowden.

German magazine Der Spiegel has published new disclosures of signals intelligence collected by the United States National Security Agency (NSA) and its "Five Eyes" partners, including the Australian Signals Directorate. The intelligence reveals new details of the directorate's efforts to track and combat Chinese cyber-espionage.

Stolen secrets: Chinese cyber spies have stolen details relating to the Joint Strike Fighter, or F-35 Lightning II.

According to a top secret NSA presentation, Chinese cyber spies have stolen huge volumes of sensitive military information, including "many terabytes of data" relating to the Joint Strike Fighter (JSF) - also known as the Lockheed Martin F-35 Lightning II.

The leaked document shows that stolen design information included details of the JSF's radar systems which are used to identify and track targets; detailed engine schematics; methods for cooling exhaust gases; and "aft deck heating contour maps".