Bungie is getting into the Halloween festivities by letting loose the spooky infection game type onto Halo 3 servers.
The spookiness will run until 10am tomorrow morning, and lets one or two of you start as Zombies before gradually infecting and bolstering your ranks with victims from the Human team.
There are a couple of variations to keep things fresh, too. Save One Bullet gives the Humans a limited ammo supply so they can't hold the Zombies at bay for ever, and Creeping Death where Zombies are slower but invisible and much more deadly.
There is also a third alternative called Creeping Rockets, where Humans get bigger weapons but Zombies are also harder to take down.
Infection games will act like regular ranked matches, and a maximum of four of you can join in a group. You will need eight people minimum to start, and cannot exceed the upper limit of 13.
Those of you who enjoy yourself will be pleased to know that Bungie plans more of these festive escapades in the future, and that any time you play these variations in Matchmaking you will save them in your Recent Games queue and be able to use them again in your Custom matches.