Microsoft said it had taken the "highly unusual step" of releasing a patch for computers running older operating systems. In Russia, the mobile phone provider MegaFon, Sberbank, and Ministry of the Interior became the next victim.
Spain's Telefonica was also hit, with several sources indicating that the telecom firm had instructed employees facing a ransomware screen to simply shut down their computers and await further instructions.
The WannaCry ransomware attack hit 10,000 organizations and companies in more than 100 countries on Friday. Attacks of this kind have spiked in the previous year, jumping from 340,665 in 2015 to 463,841 in 2016, according to online security company Symantec.
Termed as one of the largest and most crippling global cyberattacks of our time, the ransomware is believed to have infected well over two lakh systems across 150 countries.
"We have stopped this one, but there will be another one coming and it will not be stoppable by us", the anonymous researcher warned.
Finding out who was behind the malware is going to be very hard.
They exploited a ideal storm of factors - the Windows hole, the ability to get ransom paid in digital currency, poor security practices - but it's unclear if the payoff, at least so far, was worth the trouble.
"Repeatedly, exploits in the hands of governments have leaked into the public domain and caused widespread damage", Mr. Smith wrote. That affordable move redirected the attacks to MalwareTech's server, which operates as a "sinkhole" to keep malware from escaping. This is true at the national level as well as amongst businesses.
Tens of thousands of PCs at large institutions and companies have been infected, including the NHS in the United Kingdom and FedEx, stated the post.
Avivah Litan, a cybersecurity analyst at Gartner, agreed that the government is "is negligent not doing a better job protecting companies", but added that it's not like "you can stop the USA government from developing cybertools" that then work as intended.
Security officials in Britain urged organizations to protect themselves by installing the security fixes, running antivirus software and backing up data elsewhere.
Chris Wysopal, of the software security firm Veracode, said criminal organisations were probably behind the attack, given how quickly the malware spread. Don't click on links that you don't recognize, or download files from people you don't know personally.
Experts are advising infected users not to pay the ransom because it is unlikely they will get their files back. Equally, if you open a document and it asks to run macros, just say no.
In the UK Saturday night, goverment officials said computer systems were nearly completely up and running again, Vigliotti reported. For example, a hospital X-ray department using an XP-based machine might need a new version of the software that controls its X-ray machines. The other is to disable a type of software that connects computers to printers and faxes, which the virus exploits, O'Leary added.