The attacks exploit a vulnerability in outdated versions of Microsoft Windows that is particularly problematic for corporations that don't automatically update their systems.
"Please beware and take preventive steps against the malware attack", said Indonesia's information minister Rudiantara who, like many Indonesians, goes by one name. He said it was too early to say who is behind the onslaught and what their motivation was.
Chinese media reported on Sunday that students at several universities were hit, blocking access to their thesis papers and dissertation presentations.
Interior Ministry: The Russian Interior Ministry acknowledged a ransomware attack on its computers, adding that less than 1% of computers were affected. Security experts say this attack should wake up every corporate board room and legislative chamber around the globe.
"I don't believe it will have been a targeted attack, but will simply have been that the ransomware has sought out those organizations that are running susceptible devices", he said.
Security experts attributed the apparent success of the WannaCry virus to a "perfect storm" of conditions, including a well-known and highly unsafe security hole in Microsoft Windows, users who didn't apply a recent Microsoft patch and malware created to spread quickly once inside a network, be it a business, government or university.
Across an ocean, Darien Huss, a 28-year-old research engineer for the cybersecurity firm Proofpoint, was doing his own analysis.
"At the moment, we're in the face of an escalating threat", Wainwright said.
Experts said India is vulnerable as a large number of computers in the country run The Microsoft's older operating systems like XP, and have not been updated yet. Normally, such patches are reserved for organizations willing to pay for extended support.
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The phenomenon of companies failing to update their systems has been a persistent security problem for years.
WannaCry takes advantage of a vulnerability in Microsoft Windows. It seems many PCs didn't get updated, leaving them exposed to the malicious ransomware.
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 new versions of the worm will strike. It has attacked hundreds of thousands of computers, security experts say, from hospital systems in the United Kingdom and a telecom company in Spain to universities and large companies in Asia. But the kill switch couldn't help those already infected.
But, if everything is backed up, the encrypted files are not as valuable to the attackers.
Brad Smith, the technology firm's president and chief legal officer, criticised USA intelligence agencies the CIA and the National Security Agency (NSA) for "stockpiling" software code which could be exploited by hackers. Intelligence officials wouldn't comment on the authenticity of the claims.
"Those tools have been used by the hackers group, who are now demanding ransom to release the system they had hacked", he said.
Spain, meanwhile, activated a special protocol to protect critical infrastructure in response to the "massive infection" of personal and corporate computers in ransomware attacks. "But there's clearly some culpability on the part of the USA intelligence services".
But there will be other vulnerabilities to come, and not all of them will have fixes for older systems. He said most people "are living an online life", and these agencies have a duty to protect their countries' citizens in that realm as well. "Even without having an antivirus", they said. "It's a handy thing to have, but it's a unsafe thing to have".
And by "important", they're talking about your most commonly used files - including.mp3 audios and.mp4 and.avi videos;.png and.jpg images; and.doc and.txt documents. "And that's what's happening right now".