The maker of video games such as "Diablo" and "World of Warcraft" is warning players that hackers have gained unauthorized access to some online accounts.
Blizzard Entertainment says it has no evidence that the intruders acquired credit card information, billing addresses or players' names.
But hackers were able to access other data, including email addresses and answers to players' personal security questions. Blizzard says it doesn't believe such information alone is enough for anyone to gain access to its Battle.Net online accounts, which let people play with others around the world online.
The company also says hackers took encrypted versions of passwords. As a precaution, it's recommending that players change their passwords.
Blizzard, which is a division of Activision Blizzard Inc., didn't say how many accounts were affected.