Federal prosecutors have filed multiple charges against a 23-year-old South Korean man accused of running what they call the world's "largest dark web child porn marketplace."

The now-shuttered English-language site, called "Welcome to Video," contained more than 200,000 unique videos or nearly 8 terabytes of data showing sex acts involving children, toddlers and infants, according to the 18-page criminal indictment unsealed here Wednesday, and processed 7,300 Bitcoin transactions worth more than $730,000.

According to prosecutors, the vast on-line store was run by Jong Woo Son, a South Korean citizen currently serving an 18-month prison sentence in his home country after his conviction on charges related to child pornography. The site operated from June 2015 until it was seized and shut down by U.S. authorities in March 2018.

The site allegedly rewarded its members with "points" in relation to the amount of illegal material they uploaded, authorities announced Wednesday.

One user of the site, a former federal U.S. law enforcement agent, even downloaded over 50 hours worth of videos.

Son was indicted on federal child porn charges in August 2018, which remained sealed until Wednesday.

In addition to Son, more than 100 other suspects have been arrested in South Korea, while still more suspects were identified in other countries, including the U.K. and the U.S., including a Washington, D.C. man who was caught with the equivalent of 50 years worth of video footage he had downloaded.

The website ran solely on the dark web, a section of the internet that can only be accessed via a Tor browser, which is designed to protect users' tracks online and obscure digital footprints. Users could purchase videos using cryptocurrency and an annual membership was priced at 0.03 bitcoins (at current exchange rates, around $300).

Members earned points by uploading new and popular videos to the site or by inviting new members. The site sought only child sexual abuse imagery, according to prosecutors — its landing page stated in red bold type: "Do not upload adult porn." Prosecutors have also filed a related civil forfeiture case, seeking to seize Bitcoin assets held across 24 different accounts.

A notable moment in the investigation came in September 2017 when an Internal Revenue Service agent who was assisting with the probe noticed that the site's administrator had misconfigured his site, which revealed his South Korean IP address, and then ultimately revealed the identity of its owner. During the criminal probe, authorities conducted controlled buys of child porn videos from the site and eventually worked closely with the D.C. U.S. attorney's office on the investigation.

Ultimately the site was seized in March 2018, when Son was arrested by South Korean authorities. The Korean National Police Agency (KNPA) announced the arrest of a "Mr. A" from Danjin, roughly two hours southwest of Seoul, on May 2, 2018. They later confirmed to NBC News that this was Jong Woo Son.