Sony has officially revealed that sometime between April 17 and April 19, 2011, PSN and Qriocity service user account information was stolen by an unauthorized intruder into the network. They confirmed that is the reason the services were shut down.

“We are currently working to send a similar message to the one below via email to all of our registered account holders regarding a compromise of personal information as a result of an illegal intrusion on our systems,” said Patrick Seybold, Sr. Director, Corporate Communications & Social Media. “These malicious actions have also had an impact on your ability to enjoy the services provided by PlayStation Network and Qriocity including online gaming and online access to music, movies, sports and TV shows.”

“We have a clear path to have PlayStation Network and Qriocity systems back online, and expect to restore some services within a week”, he added.

As for why nearly a week took place between this revelation and the shut down of the network, Seybold explained, “There’s a difference in timing between when we identified there was an intrusion and when we learned of consumers’ data being compromised. We learned there was an intrusion April 19 and subsequently shut the services down.”

We then brought in outside experts to help us learn how the intrusion occurred and to conduct an investigation to determine the nature and scope of the incident, he added. “It was necessary to conduct several days of forensic analysis, and it took our experts until yesterday [Monday, April 25] to understand the scope of the breach. We then shared that information with our consumers and announced it publicly this afternoon.”

Source: PlayStation Blog