Codemasters has confirmed that its website had suffered an "attack" and "intrusion" last Saturday.
Personal data has been compromised.
Codemasters.com has been taken down, redirecting instead to its Facebook page. VIP code redemption for DiRT 3 and the Codemasters eStore has also been pulled.
"We advise you to change any passwords you have associated with other Codemasters accounts," the publisher has said in a statement sent out today.
Data compromised includes names, physical addresses, email addresses, phone numbers, encrypted passwords, order history for eStore, user names of Codemasters accounts, IP addresses and gamertags of Xbox Live users.
Credit card information is thought not to be compromised, however, due to not being stored on the servers.
Those who have bought Codemasters games digitally or at retail won't be affected.