Common Infected

Common Infected are the most commonly-faced enemy and the easiest to defeat. They are completely AI-controlled and fairly weak. Their strength lies in the fact they attack in groups sometimes as large as several dozen, known as hordes. While they seem capable of ignoring pain, they can still be killed as easily as a normal human can. They are capable of climbing ladders and scaling objects.

Common Infected react violently to the pipe bomb and will ignore survivors and investigate it instead.

Appearances and Action
Common Infected come in varying appearances, in both male and female. When not attacking, they are very vulnerable when sitting down, leaning on walls, or simply standing. They are easily provoked by light, sound, or touch, but are normally only dangerous in large groups or when completely surrounding a player. The heads, arms and legs can all be shot off, this happening easiest using a shotgun or hunting rifle. The Infected react naturally to gunfire in their vicinity, turning towards the sound to attack the shooter. Shooting one in the foot will cause a very different reaction than shooting one in the chest with a pump shotgun. They are often seen doing very odd things (vomiting, attacking inanimate objects, fighting each other, etc.) but begin to rush at you when they spot you.

Tactics
Common Infected are only strong in numbers. Sticking together is key to keeping them off of you and your teammates' backs. Remember that if you are concerned about using too much ammo, the pistol is an excellent choice for dealing with them, as even on expert, anywhere from 2-4 shots (1 shot to the head) will kill them.

When a horde of them begin to attack, the best tactic is to back into a corner (preferably) or a wall. Assign the front two survivors to crouch and melee continuously while the two survivors behind them stand and fire their weapons at them. This works equally as well when spit on by the Boomer.