Survival mode pits the human team against the zombie menace on an "arena style" map. The goal is simple, destroy the other team. Humans spawn on various places spread out across the map and zombies usually spawn in places out of sight from the humans (barricaded rooms, vents, one-way doors, etc).
The game begins with one zombie player (or more depending on the number of people in the server) as the Carrier Zombie . The survivors must try to fend off the zombies until all of the zombie lives are depleted, resulting in a survivor victory. The zombies' goal is to prevent being killed by survivors by killing and infecting as many of them as they can. For every survivor killed, a zombie player is added to the zombie team as well as an extra life. The zombie team shares their life count, so they must be cautious to not get killed (again) carelessly.
Any zombie player who is killed after the zombie life limit is depleted will be put into spectator mode, and can only communicate via textchat or microphone with other spectators to prevent "ghosting".