Commercially sensitive information on the $14 billion Joint Strike Fighter program, Australia's next fleet of spy planes and several of its naval warships have been stolen by hackers who breached a Department of Defence contractor, a government official has revealed.

A manager at the Australian Signals Directorate – the government's main national security cyber spies – told a conference in Sydney on Wednesday that the hackers stole 30 gigabytes of data including on the Defence projects.

ASD incident response manager Mitchell Clarke told the Australian Information Security Association conference that the ASD had codenamed the hacker 'Alf' after the Home and Away character played by Ray Meagher.

A spokesperson for the Australian Cyber Security Centre, for which Mr Clarke works, said the data was commercially sensitive but was not classified.