Sony announced today that the group "Anonymous" is responsible for the compromise of 77 million PSN user accounts. Sony's Kaz Hirai has been forwarding documents to US congress about what happened. And that is the problem, Sony still has no idea what was stolen from account holders. The server contained 12.3 million credit card numbers, 5.6 million from US accounts. During the investigation, Sony techs found a file titled "Anonymous" which when opened said "We are Legion".
Anonymous has apparently responded saying it "has never been known to have engaged in credit card theft."
More updates to come.