Sony Corp. worked for a third day Saturday to restore services to its PlayStation network as the FBI said it was looking into the disruption.
"We are aware of the reports and are investigating the Sony PlayStation matter," Federal Bureau of Investigation spokeswoman Jenny Shearer said via email. She did not elaborate.
Sony said the attack had prevented some people who received consoles for Christmas from using their new machines on the PlayStation network, which lets gamers compete with people around the world via the Internet.
"If you received a PlayStation console over the holidays and have been unable to log on to the network, know that this problem is temporary and is not caused by your game console," Sony executive Catherine Jensen said on the company's U.S. PlayStation blog.
Some customers posted complaints about the outage on the blog. "Three days without PSN. That's absurd,'' one said.
"We understand your frustration," Jensen responded early Saturday afternoon. "Our engineers are working to restore service as quickly as possible!"
Later in the day, she said the company had restored access for some users and would keep bringing more back online.
Sony declined to say how many of PSN's 56 million users had been affected by the attack.
The blog said the problems were the result of "high levels of traffic designed to disrupt connectivity and online game play," otherwise known as a distributed denial-of-service attack.
It was Sony's second recent high-profile encounter with hackers after an unprecedented attack on its Hollywood studio, which the U.S. government attributed to North Korea and linked to the release of the low-brow comedy "The Interview."
A hacker activist group known as Lizard Squad said it was responsible for the PSN outage as well as delays on Microsoft's Corp.'s Xbox network; Microsoft quickly fixed the problem.
The group has claimed responsibility for previous attacks, including ones on PSN in early December and August.
The August attack coincided with a bomb scare in which Lizard Squad tweeted to American Airlines that it had heard explosives were on board a Dallas-to-San Diego flight carrying an executive with Sony Online Entertainment.
Sony has been the victim of some of the most notorious cyberattacks in history. Besides the breach at its Hollywood studio, hackers stole data belonging to 77 million PlayStation Network users in 2011.