Son was arrested in March 2018 and authorities found around eight terabytes of videos of child sexual abuse during the arrest process.
He was found to be the operator of the website Welcome to Video – a covert online den for people who traded in clips of children being sexually assaulted. Among the victims was a child of just six months.
Authorities tracked down more than 300 other people connected to the website in a wide range of countries including South Korea, Britain, Germany, Saudi Arabia, Canada, Spain, Brazil and Australia.
Son operated the site from 2015 until March 2018, when it was taken down.