That's definitely a case where I would find some way to lock that down in at least two ways. PLCs seem to be in that "interesting/terrifying/lucrative" triangl

That's definitely a case where I would find some way to lock that down in at least two ways. PLCs seem to be in that "interesting/terrifying/lucrative" triangle to me, with the middle part being the kind of thing I would protect with layers of security. Overall, I have had to support some very odd security situations, back in the day. As an example: someone's philosophical position somehow got translated to an org-wide policy forbidding firewalls. I'll repeat that: they forbid firewalls. Because we were "open." And I had to support FTP sites. On Windows NT. I managed it without incident through layers of security and care, with watchfulness and compliance. PLCs? Yeah, I'd lock that down like crazy.