Hotel industry's confidentiality restrictions on guest information?

Hotels need to keep guest information confidential. If someone steals the front desk as a friend or family member to find a guest, the front desk staff needs to tell the guest that there is no such person. If the guest insists on not leaving, find the room number the guest is looking for and contact the in-house guest without the guest present. If anyone asks, they can tell him. If the hotel guests allow, they can reply the room number to the guests!