Law enforcement officials on Wednesday announced criminal charges against the South Korean operator of the largest child pornography site on the dark web and the arrest of hundreds of users around the world.  

The Welcome to video site was “the largest child sexual exploitation market by content volume” and was carrying more than a quarter of a million child pornography videos when it was taken down in March 2018, official sources said.

The site’s operator, Jeong Woo Song, a 23-year-old South Korean citizen, was arrested last year and is currently serving an 18-month prison sentence in Korea. He has been charged with nine counts in the United States.  

In addition, 337 users of the site in two dozen U.S. States and 11 foreign countries were arrested on charges of possessing child pornography, official sources said. Dozens of other suspects are under investigation.  

An internationally coordinated operation in the US, Spain and the UK rescued 23 underage victims who were ” actively abused by users of the site.” U.S. officials say they are working with law enforcement partners to rescue other victims.  

“Children around the world are safer because of actions taken by American and foreign law enforcement agencies,” said U.S. attorney Jessie K. Liu.  

Welcome to Video is one of the first websites where users traded child pornography using cryptocurrency. Cryptocurrencies allow users to send and receive cash anonymously. Officials said they were able to trace payments made to the Welcome video site by following the money.