The cheat code to unlock all zombie mode levels in Call of Duty: Black Ops is 3ARC UNLOCK. This code works for both the PC and PlayStation 3 gaming console.
To enter cheat codes while playing on the PC, press the RIGHT and LEFT triggers alternately or hold down the keyboard spacebar while on the main menu. After a few seconds, the game character will stand up. Leave the seat and look for a black-and-white computer terminal on the back wall. Approach the computer terminal and then enter the preferred cheat codes.
When playing on the PlayStation 3, tap the L2 and R2 buttons repeatedly until the character stands up. Leave the chair, and proceed to the computer terminal on the back wall, and then enter the desired cheat code.