When I was writing software for industrial PLCs and other controllers over five years ago I always thought that factory guys were paranoid about connecting them

When I was writing software for industrial PLCs and other controllers over five years ago I always thought that factory guys were paranoid about connecting them to the general IT system which in turn was connected to the internet. Quite specifically they were worried about viruses getting into the industrial PCs and causing production line stoppages. At the time it was just a theoretical possibility. Now it seems they were quite wise to be cautious.