A "sophisticated, state-based actor" has been trying to hack a range of Australian organisations for months and recently increased its efforts, Prime Minister Scott Morrison said on Friday.
The attacks have targeted all levels of the government, political organisations, essential service providers and operators of other critical infrastructure, Mr Morrison said in Canberra.
"We know it is a sophisticated, state-based cyber actor because of the scale and nature of the targeting," he said.
Mr Morrison said there were not a lot of state actors who could launch this sort of attack, but Australia would not identify which country was responsible.
Australia's Defence Minister, Linda Reynolds, said advice showed no large-scale personal data breaches from the attack.
The revelation comes after Reuters reported Canberra had, in March last year, determined China was responsible for a hacking attack on Australia's Parliament.
Australia did not publicly identify the source of the attack and China denied it was responsible.
A US security ally, Australia strained ties with its largest trading partner, China, by pushing for an international inquiry into the source and spread of Covid-19, which first emerged in the central Chinese city of Wuhan late last year.
