Australians have been urged to update their antivirus software in the wake of a cyber attack that has affected hospitals and companies across the globe.
The malware wormed its way into thousands of computer systems in an apparent extortion plot on Friday, shutting users out unless they coughed up a payment.
Australian organisations do not appear to have been affected by the so-called ransomware but the federal government says it is taking precautions.
"There has been no impact on the Australian health system at this stage," Cyber Security Minister Dan Tehan told reporters on Saturday.
But Mr Tehan said there would always be a risk of online attacks, despite measures aimed at beefing up Australia's cyber security.
"I cannot put my hand on my heart and say that means we are 100 per cent cyber secure," he said.
"The technology changes, the vulnerabilities change."
It's believed the ransomware was created after a powerful tool designed by the US National Security Agency was leaked into the wrong hands.
University of Melbourne cyber security expert Dr Suelette Dreyfus said the self-replicating bug had caused "chaos" at some institutions in Europe.
"When you have to shut down services at a hospital, and when your utilities are under attack, it is breeding a level of chaos that is concerning," she told AAP.
Dr Dreyfus said Windows computers that don't have the latest security patches were vulnerable to the ransomware, proving the importance of up-to-date software.
"Every institution, every consumer, every student with a laptop should make sure that their system is fully patched," she said.
"Because this would be nowhere near the international spread and depth of attack if people had run the updates that Microsoft had provided in March."
West Australian police echoed this message, advising people to update their anti-virus software and back up their important data.
Dr Dreyfus believed it was possible some Australian organisations were affected but they were keeping it tight-lipped.
"It might be that they're just being very quiet because they don't want to instil a lack of trust in their system," she said.
The attack struck at least 16 British National Health Service organisations, along with computer networks of companies and municipalities in dozens of other countries.
Several hospitals in London and other parts of England and Scotland were affected and some reportedly halted surgeries amid fears the lives of patients were at risk.
"It's an international attack and a number of countries and organisations have been affected," British Prime Minister Theresa May said.
More than 75,000 similar attacks reportedly happened in almost 100 countries, with Russia, Ukraine and Taiwan hardest hit, according to the cybersecurity firm Avast.
Spanish telco giant Telefonica and US delivery service FedEx were among the businesses affected.
Earlier on Saturday, Prime Minister Malcolm Turnbull said the government was monitoring the situation closely and stood ready to deal with cyber attacks.
The ransomware known as Wanna Decryptor is believed to be responsible.
