Prime Minister Scott Morrison says Australian private and public sector organisations are being targeted in a sophisticated cyber attack by a foreign entity.
"We know it is a sophisticated, state-based cyber actor because of the scale and nature of the targeting and the tradecraft used," Mr Morrison said on Friday.
He would not say which country was behind the attacks.
Asked if it was China, Mr Morrison said: "The Australian government is not making any public attribution about these matters.
"We are very confident that this is the actions of a state-based actor.
"We have not gone any further than that. I can't control what speculation others might engage in."
Mr Morrison said the investigations conducted so far have not revealed any large-scale personal data breaches.
Australia's security agencies are working closely with allies and partners to manage it.
"I spoke to (British Prime Minister) Boris Johnson last night about a range of matters, including this one and there are a number of engagements with our allies overnight," Mr Morrison said.
The ABC said government sources had confirmed the attacker was China, while Australian Strategic Policy Institute executive director Peter Jennings told The Australian it was "very clear" that the Asian giant was behind the cyber attack.
