Why does my dog attack the back door?

He thinks that the house is his territory.What you need to do is buy some bones from the local butcher and put them in the garden.What they do then is chew and naw on them and then bury them around the garden.That way he will then find him self and his territory out there and start to behave like a dog again , he ll be sniifing around all day and will be having a ball out there.