Massively multiplayer online role-playing-game maker Cryptic Studios (City of Heroes) has just discovered an unauthorized database access that occurred in December of 2010, according to a statement released today. The developer credits “increased security analysis” for catching the intrusion.

Affected data included “user account names, handles, and encrypted passwords.”

The statement continues: “While we have no evidence that any other information was taken by the intruder, it is possible that the intruder was able to access additional account information. If they did so, the first and last name, e-mail address, date of birth (if provided to Cryptic Studios), billing address, and the first six digits and the last four digits of credit cards registered on the site may have been accessed.” Don’t worry, everyone. In this extreme scenario, that would still leave the hackers with six credit card digits they’d have to guess.

Cryptic offers the standard advice of companies addressing subscribers whose data has been compromised: Stay vigilant and keep an eye out for suspicious activity. It’s the same old hacking story, except that this attack apparently went unnoticed for almost a year and a half. In light of that, better advice would probably be to keep track of your accounts all the time.