Sony said its PlayStation Network and Sony Entertainment Network had been disrupted by hackers in a distributed denial-of-service attack yesterday.
Sony said its systems were back online and the company was investigating the cause of the disruption.
The company has not received any report of user information being stolen, Sony spokeswoman Jennifer Clark told Reuters.
Sony said users faced difficulty accessing the PlayStation network between 8.52am and 11.18am Tokyo time yesterday (6.52pm-9.18pm ET Sunday), and the issue has been resolved.
The outage followed a distributed denial-of-service (DDOS) attack on the PlayStation network in August, for which a Twitter user with the handle @LizardSquad had claimed responsibility.
DDOS attacks attempt to cripple networks by overwhelming them with Internet traffic.
A tweet on Monday from a user with the handle @LizurdPatrol and account name Lizard Squad said: "50 RTs [retweets] and we will hit off PSN [PlayStation Network]. 50 FAVs [favourites] and we will hit off XBOX LIVE."
The Financial Times said some visitors to the PlayStation online store were greeted with the message: "Page not found. It's not you. It's the Internet's fault."
Last month, Sony's Hollywood studio, Sony Pictures, was hit by a massive hack that shut down most of the studio's network for more than a week.
Following that attack, hackers released sensitive data over the Internet, including employee salaries and social security numbers, along with high-quality digital versions of several unreleased films.
Sony's brushes with hackers date back to 2011 when PlayStation network suffered a major attack, resulting in the theft of data belonging to 77 million users.
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