<P> The WannaCry ransomware attack was a May 2017 worldwide cyberattack 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 through EternalBlue, an exploit in older Windows systems released by The Shadow Brokers a few months 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 . WannaCry also took advantage of installing backdoors onto infected systems . </P> <P> The attack was stopped within a few days of its discovery due to emergency patches released by Microsoft, and the discovery of a kill switch that prevented infected computers from spreading WannaCry further . The attack was estimated to have affected more than 200,000 computers across 150 countries, with total damages ranging from hundreds of millions to billions of dollars . Security experts believed from preliminary evaluation of the worm that the attack originated from North Korea or agencies working for the country . </P> <P> In December 2017, the United States, United Kingdom and Australia formally asserted that North Korea was behind the attack . </P> <P> A new variant of WannaCry ransomware forced Taiwan Semiconductor Manufacturing Company (TSMC) to temporarily shut down several of its chip - fabrication factories in August 2018 . The virus spread to 10,000 machines in TSMC's most advanced facilities . </P>

Who has the us blamed for the creation of the global wannacry ransomeware virus