So after surfing the net awhile i stumble apon this webpage that has a Zombie Infection Simulator on it. The concept is:

Zombies are grey, move very slowly and change direction randomly and frequently unless they can see something moving in front of them, in which case they start walking towards it. After a while they get bored and wander randomly again.

If a zombie finds a human directly in front of it, it infects them; the human immediately joins the ranks of the undead.

check it out here, its good for a laugh:
http://kevan.org/proce55ing/zombies/