Sony's PlayStation network remains offline in an outage that began as video game players unwrapped new consoles on Christmas.
Microsoft's Xbox Live service, which had also gone down, is back online but the company says some applications aren't fully functioning.
A Twitter account that calls itself Lizard Squad has taken credit for causing the disruption by overwhelming the companies' servers with a flood of Internet traffic.
A Twitter account called Lizard Squad in August also took credit for disrupting the PlayStation network and tweeted a report of a bomb on a plane carrying a Sony executive.
It's unclear if these episodes are related to the recent hack of Sony's movie division.