A massive cyber attack on Friday affected 74 countries across Europe and Russia, disrupting Britain's health system and infecting dozens of other countries around the world, Reuters reports.
According to the news agency, the hackers used tools widely believed to have been developed by the U.S. National Security Agency (NSA).
Hospitals and doctors' surgeries in parts of England were forced to turn away patients and cancel appointments after they were infected with the ransomware, which scrambled data on computers and demanded payments of $300 to $600 to restore access.
People in affected areas were being advised to seek medical care only in emergencies.
Telecommunications giant Telefonica was among many targets in Spain, though it said the attack was limited to some computers on an internal network and had not affected clients or services.
Also targeted was top Russian mobile operator Megafon, according to The Associated Press.
Pyotr Lidov, a spokesman for Megafon, said the attacks froze computers in company offices across Russia. He said that mobile communications haven't been affected.
Some Russian media also reported cyberattacks on the Interior Ministry and the Investigative Committee. The committee, the nation's top investigative agency, has rejected the claim, according to AP.
Ransomware is malicious software that infects machines, locks them by encrypting data and then extorts money to let users back in. A Telefonica spokesman told Reuters a window appeared on screens of infected computers that demanded payment with the digital currency bitcoin in order to regain access to files.
Officials and experts identified the malware as 'Wanna Cry', also known as 'Wanna Decryptor'. It exploits a vulnerability in Microsoft's Windows operating system that allows it to automatically spread across networks, which gives it the ability to quickly infect large numbers of machines at the same organization.
Microsoft issued a patch on March 14 described as critical to users of Windows to fix that vulnerability, which CrowdStrike and Splunk said should protect users from getting infected by Wanna Cry.
The NSA and Microsoft did not immediately respond to requests for comment.
The chaos in Britain's health system came less than four weeks before a parliamentary election in which national security and the management of the state-run National Health Service (NHS) are important campaign themes.
"This was not targeted at the NHS, it's an international attack and a number of countries and organizations have been affected," British Prime Minister Theresa May clarified.
"We're aware that a number of NHS organizations have reported that they've suffered from a ransomware attack," she added. "We're not aware of any evidence that patient data has been compromised."
In Spain, meanwhile, the attacks did not disrupt the provision of services or networks operations of the victims, the government said in a statement.
It was not immediately clear how many Spanish organizations had been compromised by the attacks or if critical services had been interrupted.
(Arutz Sheva’s North American desk is keeping you updated until the start of Shabbat in New York. The time posted automatically on all Arutz Sheva articles, however, is Israeli time.)