Computers around the globe were hacked beginning on Friday using a security flaw in Microsoft's Windows XP operating system, an older version that was no longer given mainstream tech support by the USA giant. "The numbers are going up, I am anxious about how the numbers will continue to grow when people go to work and turn (on) their machines on Monday morning", Europol Director Rob Wainwright said.
Wainwright described the cyberattack as an "escalating threat".
Cyber security experts said the spread of the worm dubbed WannaCry - "ransomware" that locked up more than 200,000 computers in more than 150 countries - had slowed but that the respite might only be brief amid fears it could cause new havoc on Monday when employees return to work.
Senior U.S. security officials held another meeting in the White House Situation Room on Saturday, and the Federal Bureau of Investigation and the National Security Agency were working to help mitigate damage and identify the perpetrators of the massive cyber attack, said the official, who spoke on condition of anonymity to discuss internal deliberations.
Given the attack's widespread nature, even such a small sum would stack up quickly, though few victims seem to be paying up so far. It was benign because it contained a flaw that prevented it from taking over computers and demanding ransom to unlock files but other more malicious ones will likely pop up.
Bitcoin, the world's most-used virtual currency, allows anonymous transactions via heavily encrypted codes.
Experts said the ransomware programme appears to support dozens of languages, showing that the hackers wanted to corrupt networks worldwide. The number of Aussie businesses hit has risen to three, although authorities assure Australia is not severely affected by the incident.
In a blog post late Sunday, Microsoft President Brad Smith appeared to tacitly acknowledge what researchers had already widely concluded: The ransomware attack leveraged a hacking tool, built by the U.S. National Security Agency, that leaked online in April.
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He criticised United States intelligence agencies, including the CIA and NSA, for "stockpiling" such code that could be used by hackers.
He added that governments should "report vulnerabilities" that they discover to software companies, "rather than stockpile, sell, or exploit them".
"We need governments to consider the damage to civilians that comes from hoarding these vulnerabilities and the use of these exploits", Smith wrote.
"An equivalent scenario with conventional weapons would be the U.S. military having some of its Tomahawk missiles stolen". The initial attack, known as "WannaCry", paralyzed computers running Britain's hospital network, Germany's national railway and scores of other companies and government agencies around the world.
Prime Minister Malcolm Turnbull has urged Australians to update their Windows operating systems in the wake of a global cyber attack.
The ransomware tracker counts the volume of queries made to MalwareTech's registered domain, which is a fundamental part of WannaCrypt's operations; the ransomware abandons its attack if it can connect to the previously unregistered domain.
Symantec said the majority of organisations affected were in Europe.
Currently, an estimated 200,000 victims in 150 different countries are reported to have been hit by the cyberattack.
Carmaker Renault said one of its French plants, which employs 3,500 people, wasn't reopening Monday as a "preventative step".