We have an alarm system, we have outdoor lighting, we lock all our doors and windows... but none is as effective a security system as is Cooper. He makes his rounds walking around the house and looking for trouble-- that is, looking for a reason to bark and groul and defend his (or our) territory. Problem is, he thinks his territory involves anything he can hear or see out our windows including the neighbors' houses, the street, actually the entire neighborhood. People outside (including the neighbors themselves) are targets of his aggressions. It goes without saying that visitors who ring our bell are fair game for him. And the mailman-- well, he's a daily source of rivalry for Cooper. It's amazing how violent and vicious he becomes when he sees him coming or sees him parking his truck on the street. It doesn't matter that it's just paper being thrown through our door slot, Cooper is there to guard and defend to the death.
It can be real annoying at times, especially when we try to greet a guest at the door. But have no doubt, if we ever need protection and security in this house-- Cooper is there to give it to us.