The Z-Sec (Zombie-Security; sometimes erroneously called Z-Sector) is a closer recreation of the classic Former Human, as they carry firearms; Doom 3's civilian zombies do not. Unlike the classic variations, all Z-Secs wear black uniforms and armor, excluding the pistol guard, possibly as reference to the classic shotgun guy. In contrast to the classic Former Humans, which were previously government Marine soldiers, Z-Secs were originally UAC security guards (private mercenary contractors) that were possessed and mutated by evil demonic spirits. They are considerably more difficult to deal with than the original Former Humans.