From news.sophos.com
This morning, SophosLabs is releasing a deep dive into the aftermath of a malware that, two years ago, looked like an unstoppable scourge. On the morning of May 12, 2017, organizations and individuals around the world were attacked by malware now known as WannaCry.
WannaCry’s rapid spread, enabled by its implementation of a Windows vulnerability stolen from an intelligence agency, was suddenly halted when security researchers registered an internet domain name embedded in the code – a routine research procedure that, inadvertently, tripped a “kill switch” subroutine in the malware, causing it to stop infecting computers. A small number of variants released in the following days, using new kill switch domains, were shut down using the same method.