"Service on the Battlefield Heroes free-to-play site has been temporarily halted while we investigate a security breach," reads a statement on the Battlefield Heroes website.
"Our investigation is ongoing; however, it appears that screen names and encrypted passwords associated with an early beta version of Heroes has been compromised.
"To the best of our knowledge, it appears that no personal data was compromised. No emails, account history, credit card numbers or payment methods."
The leak was one of the final acts of hacker group LulzSec, who have since announced their decision to disband after 50 days of activity.
A statement released by the group reads: "Our planned 50-day cruise has expired, and we must now sail into the distance, leaving behind - we hope - inspiration, fear, denial, happiness, approval, disapproval, mockery, embarrassment, thoughtfulness, jealousy, hate, even love.
"If anything, we hope we had a microscopic impact on someone, somewhere. Anywhere."
The LulzSec group has claimed responsibility for a number of website hacks in May and June, including The X Factor USA's contestant database, video games publisher Bethesda Softworks, SonyPictures.com and Nintendo.com.