WannaCry

The WannaCry ransomware attack occurred in 2017 and is considered the worst malware attack caused by ransomware. It targeted computers running Microsoft Windows. It spread using EternalBlue, which was an exploit developed by the NSA. EternalBlue was stolen and leaked a month before the attack. The attacks began on May 12th, 2017, and ended a few hours later. Marcus Hutchins was able to stop WannaCry by finding and registering a kill switch.

Sources:

https://sbgsmedia.in/2018/05/10/2261f190e292ad93d6887198d7050dec.pdf

https://en.wikipedia.org/wiki/WannaCry_ransomware_attack?scrlybrkr=3526ad34