An international gang of criminals allegedly cracked the computer systems of several email service providers, marketing companies that themselves offer bulk email services, to spam tens of millions of people with sometimes illegitimate products, the U.S. Attorney’s Office in Atlanta announced today.

At least two of those marketing companies are located in the Northern District of Georgia, Acting U.S. Attorney John Horn said in a press call.

Viet Quoc Nguyen and Giang Hoang Vu, both citizens of Vietnam, were indicted for their role in the breach. A federal grand jury also returned an indictment against David-Manuel Santos Da Silva, of Canada, who is charged with conspiring with Nguyen and others to money launder the proceeds of Nguyen’s computer hacking offenses, authorities said.