Look up the stuxnet story for an example of attacking air gapped machines via a USB rootkit. Spoilers: it was pulled by a state actor, took untold resources and still required physical access to the laptop of one of the engineers working on the target system.


You can extract WO wallet backups. You'll get 4 lines instead of 2. You can recreate the WO on your online machine in this way, without having to rely on a flash drive.