May 13 (UPI) -- Experts are continuing to repair computer systems after a global cyberattack using software stolen from the U.S. National Security Agency crippled thousands of computers in 99 countries across Europe and Asia.
Microsoft announced late Friday it was taking the "highly unusual step" of providing a security update for outdated Windows platforms, including Windows XP, Windows 8 and Windows Server 2003, for computers not running Windows 10.
The ransomware attack is considered the biggest in history, forcing hospitals across Britain to turn away patients and freezing computer systems at Russia's Interior Ministry. Hackers demanded victims pay a ransom that started at $300 for access to documents, photos, databases, videos and other files.
Many of the British hospitals that were victims to the attack were using the outdated software, experts said.
Russian cybersecurity firm said Russia was the hardest hit, followed by Ukraine and India. In Asia, there were reports of attacks at universities. In the United States, global shipping company FedEx said it was hit by the malware and was "implementing remediation steps as quickly as possible."
The U.S. Department of Homeland Security's computer emergency readiness team said it was aware of the attacks and warned against paying the ransom because "this does not guarantee access will be restored."
Cybersecurity experts identified the malware as a variant of the ransomware known as Wcry or WannaCry. In April, a group called ShadowBrokers, leaked malware used but the NSA to attack computer systems.