Codemasters is the latest publisher to fall foul of hackers, following recent attacks on Sony and Square Enix.
The UK-based outfit responsible for the Dirt, Operation Flashpoint and Lord of the Rings Online franchises told GamesIndustry.biz that password and login data for Codemasters.com had been compromised last week.
However, it claimed to have moved quickly to plug the breach and promised that all passwords are encrypted.
"On Friday 20th, there was an attempt to gain administrative access to the Codemasters.com website," explained a spokesperson. "This admin access may have allowed alterations to our company website.
"We responded swiftly with a full investigation to isolate the issue, bringing down Codemasters.com for a few hours to ensure no access would be possible, and returned the website after a security hole was closed. While some staff admin names were obtained, passwords were all encrypted.
"Our online team take security of user data very seriously and we are reviewing all of our websites and systems to ensure we are as safe as possible, especially as many games companies have been popular targets for this sort of activity recently."
Sony announced earlier this month that the massive security breach that downed PlayStation Network in April has cost them £105 million. Square Enix has also suffered at the hands of hackers recently, with Deus Ex and Eidos Montreal sites being breached.