Read about it here."K, a member of the SkidNP group, in an interview told us that they would bring down both Minecraft and Steam servers starting today. When asked why they wanted to attack Steam and Minecraft, K told us that SkidNP wanted to bring the vulnerabilities in Steam and Minecraft servers to the notice of the world. K added that, “Steam will be a hard target as they are smart unlike Mojang, Xbox and PlayStation.”"
When I looked it up, I also heard they are hacking EA too.