Folly to think otherwise.
Taking things offline and properly airgapped can also work, but wouldn't the cost of that exceed making specialized things and maintaining them?
We got into this situation due to cost, not ignorance. Both choices are higher cost than putting ancient devices on the internet.
If you need a computer system to be actually secure, rule #0 is absolutely ensure it cannot receive unauthorized inputs of any kind (airgapped, big Faraday cage, JB Weld all the ports, big scary guys with guns, redundant locks, blast doors, etc). Otherwise you've lost against any sufficiently motivated adversary.
While that works for Chernobyl, if you have a real world systems you might want somewhat more practical access.
Of course exposing industrial hardware directly on the internet is the other extreme, and you get what you're asking for.
Do something in between, if you even just apply normal network security you'll be ahead of the pack.
Problem is, a lot of these systems are not built by IT people. While they have a lot of quite admirable skills, it's just not their primary job, and thus they tend to lack the necessary paranoia at times.
The only exception I can think of would be for meter reading, which should be a separate, read only device with no ability to do harm altogether.
>nsa: what no, stop that
And remote access to hardware definitely makes management and maintenance a lot easier and quicker. (else you need to drive out for every minor issue)
Computer0•40m ago