'State actor' could be behind Nine Network cyber attack, tech expert says

A "state actor" is a likely culprit behind a crippling cyber attack on the Nine Network, a technology security expert has said.

The Nine Network is at the centre of the largest cyber attack on a media company in Australia's history, which has brought network's news production systems around the country to a grinding halt for more than 24 hours.

Fergus Hanson, of the Australian Strategic Policy Institute, told Today that the fact ransomware was used but no ransom demanded pointed to a government behind the incident.

"If you did get asked to pay a ransom, it might be a ransomware attack, in which case you would be looking at a cyber criminal … If you didn't get asked to pay a ransom, you may be looking at other actors, including state actors," Mr Hanson said.

"If you do actually get a call to hand over $1 million to free up your systems, then you would be looking more at a cyber criminal activity but you have to get a bit more detail to be clearer about which type of attack you've got."

He also said reports parts of Federal Parliament was under cyber attack also suggested a state-based source.

Mr Hanson said Nine's reporting of authoritarian governments around the world could have triggered the cyber attack.

The network is airing an investigation tonight about Russian President Vladimir Putin and the use of poison against overseas dissidents.

"That would be absolutely something you would be looking into. I think that type of reporting that rubs authoritarian leaders the wrong way can certainly motivate this type of attack."

Treasurer Josh Frydenberg refused to be drawn on who could be behind such an attack, but said the threat is 'very real'.

Television and digital production systems have been offline since the early hours of yesterday morning. This site, 9news.com.au, has also been affected.