I did read that some researchers demonstrated that they were able to pick up the sounds from a hard disk seeking, and thus reconstruct data from the disk, even if the computer was not connected to the internet.
There are multiple ways that data can be extracted from an airgapped system. Data can be transmitted via audio from speakers, adjusting the speed of the fans, or adjusting the speed of the hard drive, for example. It can be transmitted visually by utilizing LEDs on your computer's case or peripherals, or by altering refresh rates or flickering on the monitor. It can be transmitted electromagnetically or even magnetically by controlling currents in various wires or components. While all of these are technically possible, they require an attacker to first manage to infect your airgapped computer specific malware to perform the task, and then also set up monitor or surveillance equipment in close proximity to your computer. If your computer remains permanently airgapped, encrypted at rest, physically inaccessible and locked in your house, and you do not plug in random USB drives to it, then these attacks become essentially impossible.
There are a number of reasons I prefer to use Linux over Windows for my airgapped devices:
- Open source
- Not spyware
- Not bundled with a bunch of vaporware and other software I don't want or need
- Less intensive on resources for old hardware
- Less likely to randomly break or mess up
- Easier to perform full disk encryption
Having read the replies, my thinking is that it might be good to use tails for any significant transactions.
As these would be infrequent, one could recreate the wallet each time from the memorised seed phrase, and an online watching wallet.
This is certainly one way of doing it. Tails also supports encrypted persistent storage as mentioned above:
https://tails.boum.org/doc/first_steps/persistence/index.en.html