and, after you do that, make sure the machine has no connection to the
internet and you will be safe

This is my follow up question. I pulled the three CNC machines off my LAN
for now. Is there some way to connect my CNC machines to the office computer
so i can download Gcode and backup machine setup but do nothing else and let
nothing from the outside in? Note: The office computer is internet
connected.

Today, I have a DSL modem, then router, then a peer to peer LAN through out
the place.

Karl