A hacker group is taking credit for disrupting online service for some of the biggest video games, including Activision Blizzard’s Destiny and Call of Duty: Ghosts and titles from Electronic Arts.

Fans noticed the disruption of service yesterday. Lizard Squad, a hacker group, posted yesterday that EA games, Call of Duty: Ghosts, and Destiny were “#offline.” That’s a big problem for Destiny in particular, since this online game launched on Sept. 9 and is considered one of the biggest releases of the year. Activision is reporting spending $500 million on the launch of Destiny and other content, and the game generated $325 million in its first five days.

Bungie’s support team said in a post, “For those of you that still can’t play, or are getting frequently disconnected, we are working very hard to investigate why that might be happening..”

Activision, Bungie, and EA haven’t commented on the status of the server problems.

Hacker groups have used distributed denial-of-service (DDoS) attacks to take down game servers by flooding the network with requests.

Lizard Squad has not explained reasons for its attack.