Japanese game maker Sega has confirmed hackers have stolen the personal data of 1.29 million customers.
The company says the theft was via a website of its European unit but did not contain credit card information.
However, it says names, dates of birth, email addresses and encrypted passwords were stolen.
Sega has apologised to customers.
The incident follows a series of hacker attacks on the Japanese electronics and entertainment giant Sony in April which forced it to suspend online services for weeks, AFP reports.
Sony suffered one of the biggest data breaches since the advent of the internet, with personal data from 100 million accounts compromised.
Sega, known for "Sonic the Hedgehog", produces games for a range of consoles, including the PlayStation 3, Nintendo DS, Microsoft's Xbox 360 and Nintendo's motion-control Wii.