An NHK report explains the downed Member servers as the result of a recent system intrusion.
Andrisang is reporting that Square Enix is the latest gaming giant to fall victim to hacking after a December 13th inspection revealed evidence of illegal access to their servers. This in turn may have compromised up to 1.8 million of Square Enix's estimated 2.1 million global user database. The servers maintain user names, addresses, and phone numbers, however the silver lining here is that the credit card information is stored elsewhere on S-E's networks, nor has the company had any reports so far of suspicious activity on user accounts. The Final Fantasy developers/publishers appear to have moved quickly to notify Japanese authorities, reaching out to the Ministry of Internal Affairs and Communications (kind of their equivalent of the FCC) yesterday.
This is the latest in a string of high-profile attempts by hackers to access user information at companies like Nintendo and most notoriously Sony, whose Playstation Network service was left crippled in the wake of a hacker assault, allegedly motivated by Sony's attempts to prosecute software modder George Hotz (aka "Geohot").