
I had a BSD that developed this habit, but it was her love of the next door neighbour that had her litterally svreaming with excitment as soon aas the back door clicked prior to opening.
What I did was fence across my Garden so that only the first 20 or so feet length of the garden by its width is available to the dogs. This stopped her being able to run up and down such a long length of fence, and means I could reach her physically when she started. When she passed on I already had this in place for my breed can be noisy if not actively discouraged. There is also the added benefit of containing toileting area, and part of the garden is guaranteed poop free!!
What you consistently have to do is bring the dog in every time it barks, then give it command of quiet, and let out again, as soon as it barks, repeat. The dog will learn that it's fun is curtailed if it keeps barking. Honest it does work!
I too leave the back door open, and my lot do rush out if someone is at my front door, but I only have to call 'IN' amd they come back in and shut up, so the barking is brief, and I shut the back door if I am expecting visitors, or as now the kids from next door are traipsing in an out my house :(