The group "Lizard Squad" has claimed responsibility for attacks against servers of popular games like Destiny, Call of Duty: Ghosts, FIFA or Sims 4, which happened this weekend and still continues.
The attacks have been of the DDoS type, which you know are able to topple services by causing an overload to them, usually by the large amount of bandwidth used which prevent network connectivity.
Lizard Squad recently toppled other game networks such as the PlayStation Network and Blizzard’s servers for League of Legends and Path of Exile and which also run Hearthstone, Diablo 3 and World of Warcraft.
This is why its fame has spread in recent times although other groups do not consider them "true hackers” because they only use DDoS attacks instead of more complicated techniques.
A simple type of attack due to simple implementation and difficult to answer given it’s also based of service refusal.