well, technically, they could still attack you, they just can't actually hit you.Player vs Player is only available in one Zone called Cyrodil. So If your not in Cyrodil getting attacked, it's from an NPC not a player.
Fleshreaper wrote: »Look for the ora. Enemy NPC have a red ora when you mouse over them. Friendly NPCs are green if they can't be killed, white if they can be killed. And neutral NPCs are yellow.