Almost hundred countries, including India, were hit by a massive cyber attack which experts said was carried out with the help of "cyber weapons" stolen from the US' National Security Agency.
Government offices, banks and hospitals around the world are bracing themselves for a possible repeat of Friday's global cyber attack, while tech giant Microsoft pinned blame on the USA government for not disclosing more software vulnerabilities.
And more local computer systems are expected to be hit.
Sixteen National Health Service organizations in the United Kingdom were hit, and some of those hospitals canceled outpatient appointments and told people to avoid emergency departments if possible.
He began analyzing a sample of the malicious software and noticed its code included a hidden web address that wasn't registered.
Fellow security researcher Darien Huss, from tech firm Proofpoint, echoed MalwareTech's view.
"Many organizations, especially large corporations, use proxies and block direct Internet connections", said Didier Stevens, a Belgian security researcher and handler at the Internet Storm Center who found that those who use proxy servers might still be affected.
Oliver Gower of the UKs National Crime Agency said: "Cyber criminals may believe they are anonymous, but we will use all the tools at our disposal to bring them to justice".
Researchers discovered at least two variants of the rapidly replicating worm Sunday and one did not include the so-called kill switch that allowed them to interrupt its spread Friday by diverting it to a dead end on the internet.
- Who was behind the attack?
The spread of this ransomware is not now known, by MacGibbon said it was most likely by email.
Targets both large and small have been hit.
The real damage caused by the nightmare that is the WannaCry malware is becoming clearer in the cold light of day. Russia's Interior Ministry and companies including Spain's Telefonica, FedEx Corp.in the USA and French carmaker Renault all reported troubles.
"We have seen vulnerabilities stored by the Central Intelligence Agency show up on WikiLeaks, and now this vulnerability stolen from the NSA has affected customers around the world", he wrote.
A malware tracking map showed "WannaCry" infections were widespread. Many canceled all routine procedures and asked patients not to come to the hospital unless it was an emergency. Spain, Portugal and Russian Federation were also struck. Renault's futuristic assembly line in Slovenia, where rows of robots weld vehicle bodies together, was stopped cold.
Mr Tehan declined to provide details on the three affected companies, but said the first Australian company reported as hit was not "a government organisation or a hospital or anything like that".
Microsoft did release a patch to fix the issue in mid-March, so organisations and individuals who did not update their systems are at risk.
Speaking after a Cobra meeting on Saturday, Home Secretary Amber Rudd admitted "there's always more" that can be done to protect against viruses.
NZ cyber security officials say they'll be staying vigilant with the working week starting tomorrow.
WannaCry is said to take advantage of a NSA hacking tool, called EternalBlue, that can make it easy to hijack unpatched older Windows machines. It said less than 1% of computers were affected, and that the virus was now "localized" and being destroyed.
Wainwright said Europol was working with the Federal Bureau of Investigation in the United States to track down those responsible, saying that more than one person was likely behind it.
"I don't think it's to do with that preparedness".
"Remarkably few payments so far have been made, so most people are not paying this", Wainwright said.
"One thing that is very important to note is our sinkholing only stops this sample and there is nothing stopping them removing the domain check and trying again, so it's incredibly important that any unpatched systems are patched as quickly as possible", he warned.
But the kill switch couldn't help those already infected.
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