It is to clarify that CCTV camera cannot be completely replaced by the guard dog because the protective dog is used for securing from thieves and wild animals, while CCTV camera cannot be done this task. Therefore It is permissible to have a protective dog when needed, even with a CCTV camera, provided it is not kept in the rooms at home, but rather in a separate part of the dog's place outside the home or in the yard.
It should be noted that this ruling is only to have protective dog. Pet dog is not permitted in the Shariah for hobby.