Yeah, but it is also perfectly natural behavior tied to the herding heritage and flock instinct of the animal, so it's hard to determine if that is a sign of being overprotective, or a benign sign of protection. We had the nicest rottie around who seemed to harbor no aggression whatsoever, but he would become markedly more protective when there were people around that appeared to be strangers to us. He never attacked or even marked at anyone, but it was definitely a matter of protection. As it should have been.