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

The website, Welcome to Video, was the "largest child sexual exploitation market by volume of content" and carried more than a quarter million child pornography videos when it was taken down in March 2018, officials said.

The site's operator, Jong Woo Son, a 23-year-old South Korean national, was arrested last year and is now serving an 18-month prison sentence in South Korea. He faces a nine-count indictment in the United States.

In addition, 337 site users in two dozen U.S. states and 11 foreign countries have been arrested on charges of possessing child pornography, officials said. Dozens of other suspects are under investigation.

The internationally coordinated operation resulted in the rescue of 23 minor victims in the U.S., Spain and Britain who were "being actively abused by the users of the site." U.S. officials say they're working with law enforcement partners to rescue other victims.

"Children around the world are safer because of the actions taken by U.S. and foreign law enforcement," said U.S. Attorney Jessie K. Liu.

Welcome to Video is among the first websites where users trafficked in 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 to Video site by following the money.

"Regardless of the illicit scheme, and whether the proceeds are virtual or tangible, we will continue to work with our federal and international partners to track down these disgusting organizations and bring them to justice," said Don Fort, the head of criminal invesetigation for the Internal Revenue Service.