The hackers behind the cyberattack on the Colonial Pipeline, DarkSide, received $90 million in bitcoin ransom payments over the past nine months from dozens of online victims before shutting down last week, according to new research released Tuesday.

DarkSide is a group of organized hackers, suspected to be based in Eastern Europe, selling software hacking tools to other criminals to carry out attacks on wealthy organizations and entities. The FBI confirmed the group was responsible for the pipeline attack earlier this month that caused major oil shortages on the East Coast of the United States.