The FBI has hacked the dark web, infiltrating “the largest remaining known child pornography service in the world”.

The ‘unprecedented’ sting op saw 1,300 people arrested.

The site, known as ‘Playpen’, launched in August 2014 and allowed users to sign up and upload images, primarily for “the advertisement and distribution of child pronagraphy”.

Within a month of Playpen’s launch, the website had garnered nearly 60,000 members. By 2015 that number had jumped to almost 215,000, with 11,000 unique users visiting the site each week, and a total of 117,000 posts.

Many of those posts contained some of the most extreme child abuse images one could imagine, according to FBI testimony seen by Motherboard.

Although the website also included advice on how users could avoid online detection, a sting operation began in February 2015 when the FBI hacked into the website’s server, but decided not to shut it down.

The bureau took the ‘unprecedented’ measure of running Playpen to spy on its users and hack their IP addresses, leading to the arrests.

According to Motherboard, a public defender for one of the accused called the operation an “extraordinary expansion of government surveillance and its use of illegal search methods on a massive scale.”