Sony has now said that an intruder stole personal information about PlayStation Network users, potentially including their credit card numbers.
The news comes as the service is still offline after almost six days.
"We have discovered that between April 17 and April 19, 2011, certain PlayStation Network and Qriocity service user account information was compromised in connection with an illegal and unauthorized intrusion into our network," Sony said in a blog post Tuesday.
It was still investigating the matter, but believes that the intruder obtained names and addresses for registered PlayStation Network and Qriocity users, along with their birthdates, e-mail addresses and other personal information.
"While there is no evidence at this time that credit card data was taken, we cannot rule out the possibility," Sony said. "If you have provided your credit card data through PlayStation Network or Qriocity, out of an abundance of caution we are advising you that your credit card number (excluding security code) and expiration date may have been obtained."
In response, the company said it has now turned off both of the services -- which weren't working anyway -- and hired a security firm to conduct "a full and complete investigation" into what happened.
It now expects to restore services "within a week," the blog post says.
The PlayStation Network is used for online gaming and sales of Sony gaming software. Qriocity runs on the same network infrastructure and provides audio and video services for some of Sony's consumer products.
The problems began around midday last Thursday Japan time -- or Wednesday evening in the U.S. -- when users were greeted with an error messages when they tried to log into the services.
Sony initially expected to have the service up and running within a day or two. Last Friday it disclosed the problems were the result of "an external intrusion," and on Saturday said it was "rebuilding its network" and adding additional security.
The fact that personal data was compromised as early as April 17 suggests the hack took place a few days before users started noticing problems with the service.
Sony now advises users to "remain vigilant" and be on the lookout for e-mail, telephone and postal scams. Hackers will sometimes use personal data they have stolen to target users with phishing attacks or try to trick them into handing over further data.
"Sony will not contact you in any way, including by email, asking for your credit card number, social security number or other personally identifiable information," the company said. "If you are asked for this information, you can be confident Sony is not the entity asking."
When the services come back up, users should change their logins and passwords, which Sony said were also stolen.
"We thank you for your patience as we complete our investigation of this incident, and we regret any inconvenience," Sony said. "Our teams are working around the clock on this, and services will be restored as soon as possible."