CNN  — 

For almost three years, “Welcome To Video” was a covert den for people who traded in clips of children being sexually assaulted.

There, on the darknet’s largest-known site of child exploitation videos, hundreds of users from around the world accessed material that showed the sexual abuse of children as young as six months old.

Then it all began to unravel.

On Wednesday, the United States’ Department of Justice (DOJ) revealed how it had followed a trail of bitcoin transactions to find the suspected administrator of the site: A 23-year-old South Korean man named Jong Woo Son.

But the case is much bigger than just one man. Over the almost three years that the site was online, users downloaded files more than one million times, according to a newly unsealed DOJ indictment. At least 23 children in the US, Spain and the United Kingdom who were being abused by the users of the site have been rescued, the DOJ said in a press release.

“Children around the world are safer because of the actions taken by US and foreign law enforcement to prosecute this case and recover funds for victims,” said Jessie K. Liu, an attorney for District of Columbia where the US case was filed. “We will continue to pursue such criminals on and off the darknet in the United States and abroad, to ensure they receive the punishment their terrible crimes deserve.”

In total, 337 people from at least 18 countries who used Welcome To Video have been arrested and charged, the DOJ said. And in a statement Thursday, South Korea’s National Police Agency (NPA) said 223 of them were South Korean.

Many Welcome To Video users likely thought they were untraceable.

The site was on the darknet, the underbelly of the deep web which cannot be accessed by a regular browser. According to authorities, some customers paid for the explicit images of child sexual abuse in bitcoin, a digital currency that can be spent without users disclosing their true identity.

But the downfall of Welcome To Video shows that bitcoin isn’t as private as some cybercriminals might have thought.

What was Welcome To Video

According to the indictment released Wednesday by the DOJ, Welcome to Vid