The computer networks of Australia's major political parties were hit by a sophisticated cyber attack by a foreign country that also affected the networks of federal parliament, the prime minister has confirmed.
Scott Morrison says an investigation into a breach of the Australian Parliament House network on February 8 found the networks of Liberal, Labor and the Nationals were also affected.
A "state actor" is believed responsible for the attack, Mr Morrison said.
Security sources indicated last week China could be the source but the government's cybersecurity chief said publicly on Monday they did not know yet who was responsible.
"I do not propose to go into the detail of these operational matters, but our cyber experts believe that a sophisticated state actor is responsible for this malicious activity," Mr Morrison told parliament.
The prime minister says there is no evidence of any electoral interference.
But the government has put in place a number of measures to ensure the integrity of the electoral system regardless.
The Australian Cyber Security Centre is also available to help any electoral body or political party seeking support.
"We have acted decisively to protect our national interests," Mr Morrison said.
"The methods used by malicious actors are constantly evolving and this incident just reinforces yet again the importance of cybersecurity as a fundamental part of everyone's business."
A Liberal spokesman said the party was "working closely with security agencies" on the matter.
In March 2011, it was reported China was suspected of accessing the email system used by federal MPs, advisers, electorate staff and parliamentary employees.
Mr Morrison's comments come after Senate President Scott Ryan confirmed there had been no more breaches of the federal parliamentary computer system since February 8.
Senator Ryan last week advised that there was no evidence that any data has been accessed, but that MPs and staff were required to change their passwords.
Labor leader Bill Shorten said the attempted hacking was of "grave concern" and came after attempted infiltration of democratic processes overseas, including in the United Kingdom and the United States.
"We cannot be complacent and, as this most recent activity reported by the prime minister indicates, we are not exempt or immune," he told parliament.
Australian Cyber Security Centre head Alastair MacGibbon said unfortunately, some of the forensic evidence which could have been useful in the investigation had been removed during the action taken to stop the intrusion. The fast action also meant agencies were not certain what information the intruder may have seen or stolen.
He said agencies always had to weigh up the risk of allowing an offender to continue versus taking fast remediation action.
"We will continue to work with our intelligence and law enforcement agencies, both here and overseas, to try to determine what they were trying to do," he told reporters in Canberra.
However, he couldn't guarantee the systems were completely hacker-free, saying given the sophistication of the attack it would be churlish to say the intruder was out and would stay out.
