Researchers crack open unusually advanced malware that hid for 5 years

[Igel]

6. Sounds like it was coopting part of a separate USB drive's memory.

You plug it in, the anti-malware software doesn't see this sequestered memory. The malware runs, infects the machine, and saves data to that reserved memory, undetected.

As soon as you plug the USB thumbdrive into a networked computer, the information can be transmitted. An uninfected drive plugged into an infected machine can be infected.

The air-gapped computer is now "networked" like the computers where I worked a long time ago was "networked": Engineers ran experiments, the data was recorded on magnetic tape, and somebody would have to schlep the tapes from the experiment site to the processing section. (Okay, this was '81.)