Sony said on its PlayStation blog that its PlayStation network had been taken down by a denial of service-style attack, which overwhelmed the system with traffic, but did not intrude onto the network or access any of its 53 million users' information.
A Twitter user with the handle @LizardSquad claimed responsibility for the attack on Sunday, and said the attack was meant to pressure Sony to spend more of its profits on the network.
"Sony, yet another large company, but they aren't spending the waves of cash they obtain on their customers' (PlayStation Network) service. End the greed," one post said on Sunday.
Sony's network business has been hit by attacks before, with a security breach in 2011 dealing a major blow to plans at the time for a looser network designed to allow for the connection of a range of Sony devices.
Since then it has invested heavily in the system and is now hoping the network can serve as a centrepiece of its plans to rebuild its business after years of losses in its flagship electronics operations.
Lizard Squad said it had also targeted the servers of World of Warcraft video gamemakers Blizzard Entertainment, whose website was down. It threatened to attack Microsoft Corp's Xbox Live network, to which some users said they had problems accessing on Sunday.
"We don't comment on the root cause of a specific issue, but as you can see on Xbox.com/status, the core Xbox Live services are up and running," Xbox spokesman David Dennis told Reuters.
Blizzard Entertainment was not immediately reachable for comment, though its customer support Twitter account said the company's servers were stabilising.
Bomb scare
Lizard Squad also tweeted to American Airlines on Sunday to say they had heard that explosives were on board a flight carrying Sony Online Entertainment President John Smedley.
That followed an earlier tweet from a game player's forum telling the airline: "I'm gonna send a bomb on your plane be ready for me tomorrow".
A PlayStation spokeswoman in the United States said the FBI was investigating the diversion of the Dallas/Fort Worth to San Diego flight.
The FBI had no comment on the incident.
American Airlines said on its Twitter account that it was "aware of threats" made over the microblogging service and had alerted security.
© Thomson Reuters 2014
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