Marcus Hutchins, British cybersecurity researcher, alias, MalwareTech, was able to stop the spread of WannCry's infection. How? It was simple. He bought a website. As computers across the nation were hit by the ransomware attack which has now been tracked to North Korean hackers, panic was rampant. WannaCry, as it was nicknamed, targeted both end users and corporate servers. It managed to lock them down and it insisted on an unlock fee from all of the victims. Worse, the malware would spread the infection to other systems that weren't infected.
In spite of the fact that Microsoft issued an emergency patch for XP series, the patch was too late and many still struggled as they had the malware and couldn't move forward without paying the fee.