The name of the Mod is WaveCOM and it is a different style of XCOM, where you take your squad of 4 rookies and survive as long as you can. WaveCOM resembles quite well with the classical Survival mode approach. Over the course of the match your squad gets stronger but so do your enemies. Eventually, you will die and there is no way to finish the game, but that is what lures many players to the mode. Download it here to refresh your XCOM experience.