THE Federal Government is expected to today admit cyber thieves hacked into the computer system of a national security contractor.
ABC News reports the intruders had access to the IT network for long periods of time last year, and stole large amounts of data.
Assistant Minister for Cyber Security Dan Tehan said it was unclear who launched the incursion, and that it could be a foreign government.
"It could have been a state actor, it could have been cyber criminals, and that's why it was taken so seriously," he said.
"We're not 100 per cent sure, and that's one of the difficulties of this area."