Our Tibetan Mastiff Cody, is very protective of me and our home. He barks, growls at every person who comes into this house, other than myself and my husband. I have a large metal gate that keeps the dogs in the kitchen, master bedroom area of the house. I go out the gate to let people in and then let them meet the dogs at the gate. If it someone the dogs don't know, it takes a minute for them to calm down. Once they have sniffed them, Max and Jake are fine and shut up. Cody will bark/growl until I tell him that is enough. He will then back up enough to let them come in and watch me until I sit down. He lays at my feet, quietly, and watches every move a stranger makes. Cody had a very rough life before he was rescued and we adopted him. I love the fact that he knows what he is and what he is supposed to do and that he feels that he is home now and is supposed to be protecting us and our home. In public, he has never growled or barked at anyone. He is super at the vets office, petsmart, dog park (on the leash), craft fairs, pet fairs, etc. I trust him completely, because I know he takes his cues from me and looks at me every time he growls or barks. I got him to protect me and that is exactly what he does. I agree with everything that has been said. Your dog is maturing and just needs to understand that you are the alpha person. You also need to remember that dogs will react differently if you are alone than when your husband is around. Our Springers, both deceased, would not bark or growl at anyone or anything when Joe was home or in the car, would not let anyone come near the car or get close to me when I was alone. Friends could come over when Joe was here and pet and play with them just fine. If Joe was gone, they could come in and pet the dogs as long as they did not come too close to me. The dogs would get between us and not let them touch me. Dogs just have their own ideas of what they think is acceptable and when. Either YOU set their boundaries or they will.
Kathy