Sony said the security breach occurred at the PlayStation Store, a content download service of the network. "Although unlikely, it is possible that the passwords of a small percentage of PlayStation Network users may have been changed through unauthorized access," the company said.
As a result, intruders could have seen users' personal information and used their online "wallets" at the store, Sony said. However, because the system does not display users' entire credit card numbers, it is "very unlikely" thieves were able to steal them.
Sony said it has fixed the problem and security has been restored. The company said it is investigating the incident and is directly contacting customers who may have been affected.
To test whether their accounts have been accessed, users only have to sign in to the Internet service. People who can log on with their preset passwords have not been affected. Sony has created a support page for subscribers to ask questions and get more information.
The security breach occurred as sales of PlayStation 3 have been increasing. Shipments of Sony's latest video game console surpassed that of Microsoft's Xbox 360 in February. Sony shipped 280,800 PS3s during the month, beating the 254,600 units of Xbox shipped by Microsoft. Nintendo, however, continued to outpace its two rivals, shipping 432,000 units of the its low-priced Wii console favored by casual gamers.
Video game console sales in general were strong in February, rising to $480 million from $402.3 million the same month a year ago.