Video of Call of Duty: Modern Warfare 3's Spec Ops Survival mode (first played way back at E3) has appeared on the Interwebs, and you can watch it in action above. This segment is on the Paris map, and as you can see, players are tasked with killing incoming waves of terrorists, attack dogs and even Juggernauts, while being rewarded with funds used for extra ammo, weapons, and accessories.
In other words, it's Horde mode, done Call of Duty style. Part 2 of the video shows more of the same, including a helicopter wave, and some missile-from-above action. Spec Ops is of course all part of the game, along with singleplayer and multiplayer, when it comes out on November 8.