This is what real defense looks like:
For ideal security, law-abiding citizens could set up a computer in a room that has no RF on any frequency: no cellular communications, no FM radio, no HF radio, no Wifi, etc. The trail of electro-magnetic waves has been broken. This is the key point for near-absolute security (NAS). We have created this neologism because absolute security is impossible. In the world of electro-magnetic waves and computers, NAS is as good as it gets.
A simple room with no internet connection, with concrete walls, standard electric outlets, steel doors, and a ventilation system that does not let in RF, can be proven to be secure from RF by the use of a spectrometer.
In reality, building such a room underground might be the best decision. Special attention should be given to electrical outlets and ventilation. Certain radio waves bend, others do not. We must not allow internet connection via electrical outlet in this set up.
Inside this room, which also has good physical security, one could store private and public PGP keys and do encryption, of whatever type. One could also store encrypted files and back them up. Encrypted files made in this room could be taken to the internet via DVD-R. Once a DVD-R is used, it should be destroyed. Any computer that touches the internet is not secure at all. Best practice would be to get this secure room away from Wifi connections and any sources of RF as much as possible.
Who would actually need such a protected room? Someone running a political campaign, an inventor, an important lawyer, a business negotiator, a celebrity, any important decision maker, anyone who insists on privacy. Privacy is still not illegal in most places in the world.
Sound and RF can be more difficult to eliminate than what one might think. The angularity of the walls is designed to stop waves that bend. For example, waves around 900 MhZ are very good at bending. The concrete walls should be at least 8 inches thick. The spectrometer is important because it will tell you if your design has worked. Even though the design works and RF is eliminated, one should not bring a mobile device into the private room. A mobile device inside the private room could be attacked by a malicious actor targeting that device with intense RF. But if that happened, the spectrometer would show it immediately. All mobile devices should be left far behind before going to the secure private area. The doors are going to be crucial in determining if RF is eliminated. Common steel doors should be enough as long as they are properly fitted, especially on the bottom.
In real life, such a secure, private room could have many important uses: as a storm shelter, as a place to store firearms so that they are not accessed by children, etc. If you go to the trouble of creating such a place, you might as well pay close attention to the ventilation and thickness of the walls– and make it suitable as a nuclear bomb shelter.