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CISA Releases Guidance Urging Water Treatment Facilities to Disconnect Equipment From the Internet
(www.privacyguides.org)
This is a most excellent place for technology news and articles.
The things you mentioned probably aren't the problem. It's not hard or expensive to setup secure remote access for systems.
The real problem is that a lot of this very expensive and very specific infrastructure equipment is also very old, and frequently does not support newer and more secure protocols.
Source : I've been trying to get gas generators to fire off email alerts using modern authentication with conditional access for about a week now.