Marcus Hutchins is the 23 year old cybersecurity researcher who is credited with finding the killswitch to the WannaCry ransomware attack.
He was arrested yesterday (August 2, 2017) at the airport when he was preparing to leave the U.S. after attending the DefCon hacking conference in Las Vegas. His arrest is reported on Motherboard.
The July 11, 2017, Indictment alleges that Hutchins was involved with the Kronos banking trojan. Of course, Kronos malware can only do evil if it is installed on the target systems. Like so much malicious software, Kronos is installed through phishing email attacks.