I've looked into security cameras on several occasions for the reason that if guests break house rules, then, you need evidence to back up any claim you have against them. Understand this: Guests are not under surveillance by the use of CCTV cameras, the cameras are there because Airbnb require Hosts to provide evidence of any damages, over occupancy, unregistered visitors, altercations, claims or whatever complaint may be brought. CCTV is a good way to provide this.
This being said, there are rules:
It's absolutely crucial info for every host who has either interior or exterior cameras to be fully aware of, as Airbnb can - and regularly do - suspend/delist hosts if a scamming/disgruntled guest complains about the cameras, and the host hasn't disclosed them in all the right places.
Regardless of personal opinions on whether or not hosts should have cameras indoors, they are permitted by Airbnb, as long as they're not in bathrooms and sleeping spaces. (personally, I'd never stay in a place with indoor cams, but can see where they'd maybe be necessary in a shared home environment where a host is not on site).
All cameras of any type must be disclosed, even if turned off/not operational (including cameras on computer monitors, nanny cams, baby monitors etc).
All it takes is one complaint from a vengeful guest about any undisclosed monitoring/surveillance device, and the host is toast.
In the app, go to: Booking Settings > House Rules > Details Guests Must Know About Your Home > Surveillance or Recording Devices on Property. Slide the button to the On/Yes position.
Then: "Describe any device that records or sends video or audio, or still images. Specify each device's location and whether it will be on or off."
This message will then appear in a pop-up box that the guest agrees to accept in order to complete the booking (like the House Rules).
This provides what Airbnb considers sufficient disclosure at the time of booking, per their TOS, without having to wonder if a guest read the listing description in its entirety to catch it.
This specific procedure is mandatory. Failure to use the Surveillance button for disclosure can get you delisted. It is still a good idea to include surveillance information in your written listing description, written House Rules, listing photos, and any messaging with the guest.
It's also mandatory to notify any existing future reservations of the fact that you added a camera, and its location.
Existing reservations can choose to cancel for free because if this change in terms post-booking. But you can mitigate their option to cancel by offering to remove the cameras for their stay. I would photograph or film yourself doing so, for the purpose of documenting that you did.