Treyarch has announced today that the popular zombie mode (which first made an appearance in Call of Duty: World at War) will be coming to the next game in the series, Call of Duty: Black Ops. Treyarch called it one of the "worst kept secrets." A teaser site has also been launched that shows off zombie mode.

Four players will be able to face zombies in the co-op mode, and the company claims that the mode has been improved: "We've taken extra special care to retain the essential ingredients of our Zombie game, and have also crafted a nice surprise for the fans."

Zombie mode was first introduced in Treyarch previous title, Call of Duty: World at War. The feature was a big hit, and the studio hopes they made it even better in Call of Duty: Black Ops.

The game is set to hit retail store shelves on November 9th for the Xbox 360, PlayStation 3, Wii, PC, and DS.