Using offline updates requires strict discipline. A single infected USB drive can compromise your air-gapped network.
An antivirus from six months ago is almost as bad as no antivirus at all. Keep your ESET offline updater fresh, and your air-gapped machines will stay safe.
SOURCE: EXTERNAL. INITIALIZING... LOADING UPDATE FILE: NOD32_V92.0.12.SIG
The screen flashed red. SIGNATURE FILE CORRUPTED. INTEGRITY CHECK: FAIL.