Hundreds of people in nearly 40 countries, including over 50 Americans, were arrested for accessing the darknet child porn site “Welcome to video,” which ran on cryptocurrency.

The “world’s largest” dark web porn site that boasted “over a million” downloads has been shut down after international authorities said they were following a battered trail of Bitcoin transactions.

Jong Woo Son, 23, a South Korean citizen, was indicted by a Federal Grand jury in 2018 for running Welcome to the video, which authorities described as “the largest child sexual exploitation market by content volume,” according to the justice Department. The son was sentenced to 18 months in prison in Korea; however, the nine-count indictment against him was not unsealed until Wednesday. 

The site, which allegedly operated from at least June 2015 to 2018, had more than 200,000 unique videos, amounting to more than eight terabytes in size, according to the indictment obtained Oxygen.com over the course of three years, authorities said the site received at least 420 Bitcoins through 7,300 transactions – the equivalent at the time of about $ 370000.

“Darknet sites that profit from the sexual exploitation of children are among the most vile and reprehensible forms of criminal behavior,” assistant attorney General Brian A. Benchkowski of the justice Department’s criminal division said in a Press statement. 

The reach of the Darknet site supposedly spanned the globe. Three hundred and thirty-seven people were arrested in 38 countries, including the United States, Korea, Canada, the Czech Republic, Germany, Saudi Arabia, Ireland, Spain, Brazil and other countries. A total of 23 children who were “actively abused” by users of the site were also rescued in the US, UK and Spain during the investigation, officials said.

Fifty-three people in the US have been charged as part of a wide-ranging investigation, two of whom died by suicide after authorities executed search warrants on their property.

U.S. federal employees, investigators said, were also implicated in the dark web child porn investigation, according to the indictment. Former ICE special agent Richard Nikolai Gratkowski and border patrol agent Paul Casey Whipple, both of Texas, were arrested on child porn charges in connection to Welcome to Video. Gratkowski, 40, who pleaded guilty to intent to access child porn, was sentenced to 70 months in prison and ordered to pay $35,000 in restitution to seven victims. Whipple was also charged with production and distribution of child porn. The 35-year-old is in custody while his case is pending. 

Son was arrested by Korean, American and British authorities on March 5, 2018. The 23-year-old was previously identified after law enforcement discovered the Welcome video did not hide the IP address of his server, which they later learned was registered in his name. Authorities seized the server Dream, which was hundreds of thousands of videos with child porn. The national center for missing and exploited children is currently combing through a mountain of content. 

The site, described by officials as “one of the first of its kind to monetize” child porn using Bitcoin, was driven – and funded-by cryptocurrency. Some of the accounts that allegedly funneled money to the site reportedly also laundered funds to other darknet sites, including Agora, AlphaBay, and the shady drug port silk road. 

“Unfortunately, advances in technology have allowed child predators to hide behind the dark web and cryptocurrencies to further their criminal activities,” said Alasa Erichs, acting Executive Deputy Director for National security Research, in a Department of justice press Statement. 

Investigators tracked Bitcoin payments on a dark website using cryptographic metadata – or blockchain-that contains records, timestamps and data on cryptocurrency transactions. The site’s six-month VIP subscription, which gave users unlimited access to child porn videos, reportedly cost 0.03 bitcoins – about $350. 

“Through sophisticated tracking of Bitcoin transactions, IRS-CI special agents were able to locate the Darknet server, identify the website administrator, and eventually track the physical location of the website’s server,” said don Fort, IRS chief of criminal investigation.

Before it was taken down by authorities, the site’s welcome page specifically warned users: “Don’t download adult porn.”

An undercover Federal agent has repeatedly used Bitcoin to access Welcome to Video content. In one case, an investigator noticed a man performing sex acts on a 6-month-old child, according to an indictment against a dark web platform. That particular video, officials said, has been downloaded 113 times. Another video showing a man urinating on a 10-year-old girl has been downloaded 219 times. 

In 2014, the national center for missing and exploited children received 1.1 million reports of incidents involving child pornography. But in a few years, that figure has skyrocketed to more than 18 million in 2018.

The rise of cryptocurrencies and the dark web has created an anonymous, growing and limitless criminal market that governments around the world have at times tried to add to.

“It was popular with criminals in certain circles on the darknet,” Eric wall, a Swedish Bitcoin researcher, said Oxygen.com. 

“Some have switched to more private cryptocurrencies, but Bitcoin is sometimes still retained as an option. Cryptocurrencies are popular not only because they give you the privacy of how much you have or what you use it for, but also because it’s impossible to take from you when you use it correctly. It’s a very powerful thing .”

Wall, a former blockchain leader at Nasdaq-owned FINTECH company Cinnober, noted that cryptocurrency crime has actually declined in recent years, especially after the silk road drug platform was first shot down by the FBI in 2013.

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