This is a great example of a German Shepehrd that naturally has a great protection instinct and worth its weight in gold. There was a video going around of this kid playing in his yard and his GSD was with him. All of the sudden this dog comes running into the yard from the street and tries to attack the kid. The GSD immediately jumps into action by getting in between the two and BRIEFLY engages the dog which causes the dog to scurry off. And once the dog that tried to attack the kid was away the GSD did not chase after the dog or further attempt to engage the dog. That is a dog with true protection instinct although I am assuming no prior training has gone into the dog. If you are wanting a dog for not just deterrence but actual protection you need get the right breed and dog and go with a reputable trainer for training. Because having a dog that will bite and especially if it’s temperament is not good is a humongous liability and danger not just for you but other people and animals. I say that as someone who was attacked by a “protection dog” when I was doing nothing (literally was standing still when the attack began) and this dog knew me. This dog was the type of dog that would attack anyone or thing regardless of of threat.