The United States has indicted six Russians for scamming websites including the popular adult site Pornhub out of $36 million through a network of bots that spread fake ads.

The U.S. Justice Department on Tuesday charged a group of eight foreign nationals, including six Russians, with committing “sophisticated” digital advertising fraud. The U.S. alleges the suspects “represented to others that they ran legitimate companies that delivered advertisements to real human internet users accessing real internet webpages” between 2014 and 2018.

“In fact, the defendants faked both the users and the webpages,” reads the indictment, describing a network of automated bots mimicking real users clicking on online ads.

The Russian nationals used a type of malware that powered a three-pronged operation to infect websites including Pornhub, according to the indictment and an extensive investigation published by the U.S. news website BuzzFeed.

“Many of the millions of computer users who downloaded the malware became infected after being tricked by misleading ads appearing on websites including the hugely popular adult site Pornhub,” BuzzFeed reported.

The world's largest pornography website has been blocked in Russia for more than two years based on a decision by the Roskomnadzor media watchdog.