How did Sony let down its guard to allow a hacker to steal the personal data of 100 million online gamers? In a letter to Congress, Sony says the hacking group “Anonymous” is indirectly responsible for the theft. Apparently, Sony was battling a denial-of-service attack from Anonymous when the theft went down; the group was seeking retaliation against Sony for taking a hacker to court in San Francisco. It is unclear, however, if Anonymous and the hacker who stole the data were working together. "Whether those who participated in the denial-of-service attacks were conspirators or whether they were simply duped into providing cover for a very clever thief, we may never know," Sony's letter said.