Authorities in the U.S. have taken down the ‘largest’ darknet child porn website after tracing bitcoin transactions on the blockchain to identify its operator.

According to an announcement published by the Department of Justice, a total of 337 alleged pedophiles were arrested in 38 countries, and 23 children were rescued from abusive situations thanks to the operation.

The darknet website, Welcome to Video, was reportedly running since June 2015, and hosted 8 terabytes of child pornography. These 8 terabytes reportedly included 200,000 videos where children and infants in sex acts, the criminal indictment notes.

The website ran on the dark web and saw users pay a six-month membership fee of around $350 worth of bitcoin for access to its content, and allowed for unlimited downloads. The DOJ reportedly traced bitcoin payments using the blockchain to find both users and administrators of Welcome to Video.

The darknet platform created a unique bitcoin address for each user, and in total according to Chainalysis 1.3 million BTC addresses were found registered, which could mean it had over one million users. Chainalysis’ blog post reads:

When law enforcement shut down the site, they siezed over 8 terabytes of child pornography, making it one of the largest siezures of its kind. The site had 1.3 million Bitcoin addresses registered. Between 2015 and 2018, the site received nearly $353,000 worth of Bitcoin across thousands of individual transactions.

After tracking the bitcoin transactions on the blockchain, the DOJ was able to identify the website administrator, who was running payments through a unnamed American cryptocurrency exchange.

Thanks to the exchange’s know-your-customer (KYC) checks, the website’s administration was registered on it with his real name cell phone number, and email account. He was identified as South Korean man Jong Woo Son.

Son was already serving an 18-month sentence for child pornography charges in South Korea, after the website’s servers were found when authorities raided his home. Now over 100 suspects have been arrested in South Korean in connection to the website, and at least five U.S. citizens were found guilty and sentenced for child pornography charges.

Speaking to NBC News the Korean National Police added:

Most of the users were in their 20s, unmarried and white-collar office workers and first-time offenders, although some were ex-convicts of sexual crimes including juvenile sex offenders. One possessed as many as 48,634 child porn [files].

Welcome to Video explicitly asked users to “not upload adult porn” in its front page. As reported last year Korean authorities seized $1.4 million in bitcoin after the country’s Supreme Court ruled cryptocurrencies can be forfeitable assets. The funds were seized from a criminal who distributed child porn. – potentially Son himself.