A couple years ago I worked on a service that had to communicate with a Siemens S7-1500 PLC. Based on my experience with that project, none of what I’ve read recently about unsecured industrial PLCs is surprising. I opened Siemens TIA Portal and PLCSIM for the first time and thought “wow, I didn’t think the Windows 95 GUI library was still supported.” None of the PLC contractors we had hired knew how to enable TLS on…
Most factories I know do not allow their PLC be accessed from the internet. They are usually on a separate Network. However, the "engineering" station (the computer running e.g. TIA Portal) sometimes is. The PLC engineers I had contact with usually had an electrical engineering background. That's why they like PLCs in the first place with the ladder logic programming languages, grafcet and if they feel fancy a bit of…
Then someone plugs in a cable because boss wants something "over there" and there's already a network that runs "over there". Or optimizes to a smart switch with vlans, and then someone else optimizes to a single vlan. It's not hard to not give a shit, or not understand, network security.