Blizzard has issued a security warning detailing "an unauthorized and illegal access" of their internal network, urging customers to change their passwords for the battle.net service, even if they haven't fallen victim.

The announcement explains that the data accessed includes "the answer to the personal security question" and a list of email address for players on North American servers, as well as "information relating to Mobile and Dial-In Authenticators", but goes further to explain that none of this information by itself would be enough for someone to gain access to an account, and that to their knowledge no credit card details or other financial information was compromised.

Even when you are in the business of fun, not every week ends up being fun. This week, our security team found an unauthorized and illegal access into our internal network here at Blizzard. We quickly took steps to close off this access and began working with law enforcement and security experts to investigate what happened.

At this time, we’ve found no evidence that financial information such as credit cards, billing addresses, or real names were compromised. Our investigation is ongoing, but so far nothing suggests that these pieces of information have been accessed.

Blizzard also detail in the announcement that "cryptographically scrambled versions of Battle.net passwords (not actual passwords) for players on North American servers were taken".

You can read the full statement over here, and ensure you change your battle.net password as soon as possible.