A zombie using the default texture pack.

Zombies are your worst enemy. They will stop at nothing until you are dead, and all of your inventory is spilled all over the floor! Only you can stop them, with sword in hand!

Zombies spawn at night, and in areas with a low level of lighting. They can kill the player in an average of three hits, unless said player is wearing a good-condition suit of armour. Zombies, along with all other aggressive mobs, cannot spawn unless they are further away from you than 25 blocks. This gives you an advantage; when they spawn, they are unable to detect the player from such a distance, thus allowing them to flee before they have been detected.