A massive hacking attack infected tens of thousands of computers around the globe with so-called ransomware Friday, encrypting data and demanding ransom payments in order to restore access. The attack reportedly affected a number of U.K. health care facilities, public transport systems in Germany and even the computers of the Russian Interior Ministry.
Altogether, the attack may have infected more than 75,000 computers in countries around the world, according to estimates from antivirus software vendor AVG Avast.
Affected computer systems forced emergency rooms in the U.K. to turn away patients. Spains Telefonica disclosed that some of its computers had been impacted. Russia’s Interior Ministry reportedly had more than 1000 computers rendered unusable by the attack. Multiple German Twitter users posted photos of public transit signage that had been hacked.
Ransomware is nothing new. Enabled by the cryptocurrency bitcoin, virus writers have for some time pressured PC users into paying them hundreds of dollars to regain access to their data. But Friday’s attack seemed to spread more quickly than any other, and has already been called the largest such attack to date.
The attack had been made possible by a Windows security flaw that was apparently first discovered by the National Security Agency (NSA), which had been collecting these kinds of vulnerabilities to use for covert surveillance. The NSA’s cyber arms cache was leaked last month by Wikileaks, and Microsoft has since released a patch — but countless computers remain unpatched.