Square Enix has issued a statement warning that one of its servers has been hacked.
The server in question relates to the Square Enix Members service, which is available for free to its customers in North America and Japan.
The company began a temporary suspension of the service at 10pm PST on December 12, and estimated that it would last for "a few days" while the matter was investigated and counter-measures were taken.
"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," the statement read.
"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."
Several game companies have been targeted by hackers this year, including Sega, Codemasters and Valve. The most famous example is the attack on Sony in April, which resulted in the PlayStation Network being taken offline for a month while new security measures were put in place.