Show Hide image 5 May 2011 Sony hack: vigilante group implicated PlayStation hack made possible by online group Anonymous' own attack, Sony claims. Sony has blamed an online vigilante group for their indirect involvement in the recent PlayStation Network hacking. The online gaming system was breached on 20 April leading to the theft of 77m user details, with further data from 25m users following shortly after. In a letter to the US House Commerce Committee, Sony has accused the Anonymous group for allowing the breach to occur, saying it was busy fighting overwhelming traffic from the group when the hacker struck. The supposed 'denial-of-service' attack temporarily disabled Sony's system by bringing down its servers. Anonymous deny any involvement in the data hacking, though Sony claim the attack was a response to federal court action levelled against a hacker from the vigilante group. Sony said that a planted file has since been found on one of its servers; named after and suggesting Anonymous' responsibility. The file also featured the group's often-used phrase "We are legion." In the letter Sony added: "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." By Alice Gribbin Alice Gribbin is a Teaching-Writing Fellow at the Iowa Writers' Workshop. She was formerly the editorial assistant at the New Statesman.