Square Enix has announced that unknown parties has gained unauthorized access to a server related to Square Enix Members and therefore they have taken down the service in Japan and North America. Europe is not affected by the hack.
They said that it might take a few days to look into the matter and fix the security holes.
You can read the full statement below.
We have reason to believe that unknown parties may have gained unauthorized access to a particular Square Enix server related to the free SQUARE ENIX MEMBERS service offered in North America and Japan. In response, Square Enix, Inc. has temporarily suspended operation of the SQUARE ENIX MEMBERS service starting at 10PM (PST) on December 12, 2011.
We are assessing the full extent of this potential breach to determine what data, if any, was compromised and will provide more details as soon as possible. While some personal information may have been accessed, we can confirm that there is no possibility of any credit card information leak from this incident, since the server in question stores no credit card information. We estimate that the suspension will continue for a few days until we complete our investigation and counter-measures. We will update you as we learn more.
We sincerely apologize for any inconvenience caused by the temporary suspension of the SQUARE ENIX MEMBERS service. We take data security extremely seriously and we regret any inconvenience this may have caused our customers and fans. We appreciate your patience and support at this time.
