content: and how he stopped WannaCry by figuring out it had a kill-switch  He registered the domain because he figured out it would stop WannaCry from spreading. Edit: My comment is wrong. MalwareTechBlog posted this tweet: "I will confess that I was unaware registering the domain would stop the malware until after I registered it, so initially it was accidental. So long as the domain isn't revoked, this particular strain will no longer cause harm, but patch your systems ASAP as they will try again."