Battle.net has tons of users. Blizzard (the folks who brought you WoW, StarCraft and Diablo) posted on the Blizzard website that it discovered an unlawful and unauthorized breach into its internal network, on August 4th.

The following have been compromised (stolen), but there’s no evidence that credit card info was stolen:

• A global list of email addresses of Battle-net users
• For North-American players, which includes Latin America, Australia, New Zealand and Southeast Asia), the answers to the personal security question, and information about Mobile and Dial-in authenticators were accessed as well.
• The encrypted passwords of players on North American servers have also been dumped by the attackers.

So… don’t panic. Check out with Blizzard what to do… like change your password,  change your secret questions and answers.

I’d suggest going a bit farther: Keep a close check on your credit card report, and since you might have used the same password/questions and answers elsewhere, change them, and change that practice, too! Also, watch out for phishing attacks since your email addresses have been compromised.

Source:

http://www.ghacks.net/2012/08/10/blizzards-battle-net-hacked-change-your-passwords-now/?_m=3n%2e0038%2e607%2ehj0ao01hy5%2emdc