Details of the multi-billion dollar Joint-Strike Fighter and P-8 surveillance plane programs were among information stolen from an Adelaide-based Australian Defence Sub-contractor by hackers, possibly working for a foreign government.

Intelligence gathering unit the Australian Signals Directorate was involved in forensic analysis of the attack after it was alerted a hacker had been inside the subcontractor's computer system for five months.

And they didn't have to work hard to get in - reportedly, the system's username was 'admin', and the password was 'guest'.