The U.S. Department of Justice announced that it had indicted two Vietnamese men for hacking into email services and stealing 1 billion email addresses and other confidential information, resulting in what’s believed to be the largest data breach in U.S. history.

Assistant Attorney General Leslie Caldwell said in a statement that the attacks, running from February 2009 to June 2012, resulted in the largest data breach of names and email addresses “in the history of the Internet."

According to the DOJ, the defendants then sent spam emails to tens of millions of users, generating US$2 million in sales.

Viet Quoc Nguyen, 28, of Vietnam, allegedly hacked into the email service providers, stealing proprietary marketing data containing more than 1 billion email addresses, the DOJ said. Nguyen, along with Giang Hoang Vu, 25, also of Vietnam, then allegedly used the data to send spam messages, the agency alleged.

David-Manuel Santos Da Silva, 33, of Montreal, was indicted for conspiracy to commit money laundering for helping Nguyen and Vu to generate revenue from the spam emails and launder the proceeds.

The DOJ said in the indictment that Nguyen and Da Silva made approximately $2 million for the sale of products derived from Nguyen’s affiliate marketing activities between May 2009 and October 2011.