The WannaCry Ransomware attack was a worldwide cyberattack in May 2017 by the WannaCry ransomware Cryptoworm, which targeted computers running the Microsoft Windows operating system by encrypting data and demanding ransom payments in the Bitcoin cryptocurrency. It propagated by using EternalBlue, an exploit developed by the United States National Security Agency (NSA) for Windows systems. EternalBlue was stolen and leaked by a group called The Shadow Brokers a month prior to the attack. While Microsoft had released patches previously to close the exploit, much of WannaCry’s spread was from organizations that had not applied these, or were using older Windows systems that were past their end-of-life. These patches were imperative to cyber security, but many organizations did not apply them, citing a need for 24/7 operation, the risk of formerly working applications breaking because of the changes, lack of personnel or time to install them, or other reasons.
The attack began at 07:44 UTC on 12 May 2017 and was halted a few hours later at 15:03 UTC by the registration of a kill switch discovered by Marcus Hutchins. The kill switch prevented already infected computers from being encrypted or further spreading WannaCry. The attack was estimated to have affected more than 300,000 computers across 150 countries, with total damages ranging from hundreds of millions to billions of dollars. At the time, security experts believed from preliminary evaluation of the worm that the attack originated from North Korea or agencies working for the country. In December 2017, the United States and United Kingdom formally asserted that North Korea was behind the attack, although North Korea has denied any involvement with the attack.
A new variant of WannaCry forced Taiwan Semiconductor Manufacturing Company (TSMC) to temporarily shut down several of its chip-fabrication factories in August 2018. The worm spread onto 10,000 machines in TSMC’s most advanced facilities.