An extensive cyberattack struck computers across a wide swath of Europe and Asia on Friday, and strained the public health system in Britain, where doctors were blocked from patient files and emergency rooms were forced to divert patients. Attacks were being reported in Britain and 11 other countries, including Turkey, Vietnam, the Philippines, Japan, with the majority of affected computers in Russia.
The attack involved ransomware, a kind of malware that encrypts data and locks out the user. According to security experts, it exploited a vulnerability that was discovered and developed by the National Security Agency.
The hacking tool was leaked by a group calling itself the Shadow Brokers, which has been dumping stolen N.S.A. hacking tools online beginning last year. Microsoft rolled out a patch for the vulnerability last March, but hackers took advantage of the fact that vulnerable targets — particularly hospitals — had yet to update their systems.
The malware was circulated by email; targets were sent an encrypted, compressed file that, once loaded, allowed the ransomware to infiltrate its targets.

Reuters reported that employees of Britain’s National Health Service were warned about the ransomware threat earlier on Friday.

More at: nytimes.com