Sony’s PlayStation Network was knocked off line on Sunday.

The site was allegedly hacked by a group called "Lizard Squad.” They also took credit for several other major game network hacks.

Sony's official PlayStation Twitter account acknowledged the problem, saying in a message that "We are aware of the issues some users are experiencing, and are working to address them."

It marks the second attach on the network. In late November, the Sony Pictures Entertainment division was infiltrated by a group called #GOP (Guardians of Peace), which leaked "top secret" data—including the personal details of current and former employees, as well as some A-list celebrities.

Lizard Squad tweeted on Dec. 1, suggesting more mayhem is in the works: "Microsoft will receive a wonderful Christmas present from us.”

See the below video.