In October, the Norwegian hacker Einar Otto Stangvik exposed the largest and most well-known dark web portal for the sexual abuse of children through a great deal of patience, creative ideas, and a simple technological trick.

But Stangvik and his colleagues at the newspaper VG could hardly believe what they discovered this past January: The forum Childs Play, which had more than a million users worldwide, was run by a task force of the Australian police.

For eleven months, the Australian investigators monitored the site for information about perpetrators, victims, and users. Just a few weeks ago, the portal was taken down.

It wasn't the first time that Stangvik, who used to work as an IT-security expert for various Norwegian companies, had dug around the darker corners of the web to hunt down backers and perpetrators of child pornography. Back in 2015, he used a program he'd written himself to unmask 95,000 users worldwide who had downloaded photos and videos online.