Sega joins the growing list of company's that have fallen victim to cyber attacks after warning users that personal data may be at risk.
The game maker said in an email yesterday that email addresses, dates passwords had been accessed by hackers.
Passwords were encrypted and no financial data was accessed, it said.
Sega joins a growing list high profile company's that have been hit in recent weeks by cyber crime.
On Wednesday the public website of the CIA went down, with the hacker group Lulz Security saying it had launched the attack.
Although the group fashions itself more as pranksters and activists than people with sinister intent, its members have been accused of breaking the law and are wanted by the FBI and other law enforcement agencies.
Lulz broke into a Senate website over the weekend and released data stolen from the legislative body's computer servers.
In May, the group posted a fake story on the PBS website saying that rapper Tupac Shakur was still alive and living in New Zealand.
The group denied any involvement in the Sega case, however, asking Sega to instead contact them to help destroy the hackers that attacked you.
But it does underline mark an uptick in crime over the Internet
The last high-profile victim was the International Monetary Fund this weekend, who's computer network was breached by what was believed to be a government backed effort.
Just last week banking giant Citibank confirmed that credit card data of about 200,000 of its North American customers have been hacked. The event marked the largest attack on a bank in the US to date.
The week before US military contractor Lockheed Martin was compromised as hackers used Lockheed's own secure id technology to access its networks.
Google has accused Chinese hackers of targeting the Gmail accounts of U.S. government officials.