PlayStation Network temporarily shut after attack - Update
Sony has confirmed on the official PlayStation Blog that it turned off the PlayStation Network (PSN) and Qriocity services on Wednesday 20 April after there had been an "external intrusion" which affected the services. The company says it needs to have the systems offline while it is conducting an investigation. As of writing, the systems are still unavailable. Early reports from Sony suggested a DDoS attack was in progress, but those messages have since been removed.
Suspicion had initially fallen upon Anonymous who had previously launched attacks upon Sony as part of "Operation Sony" (Opsony), a payback attack for Sony's legal action against George Hotz (Geohot) – since settled – and Alexander Egorenkov (Graf Chokolo). But, a statement on Anonymous' news service says "For once we didn't do it", though it doesn't rule out the possibility other members of Anonymous could have taken action. It says that it thinks "a more likely explanation" is that Sony are covering up an internal problem with the company servers.
Update - According to a further posting from Sony on Sunday 24 April, the systems are still suspended and the company is "working around the clock to bring them both back online". The delay is due, now, to Sony "rebuilding out system to further strengthen our network infrastructure".