Halil, for a small water utility, the physical consequence is not abstract: if an attacker gets from a public-facing PLC/HMI into pump or valve control, you can get tank overflow, loss of pressure, chemical dosing errors, or forced manual operations. The evidence we have supports the core pattern: CISA says Unitronics PLCs in U.S. water/wastewater were actively exploited through poor password security and internet exposure; the FBI/CISA/partners advisory says IRGC-affiliated “CyberAv3ngers” targeted internet-accessible Unitronics Vision Series PLC/HMIs with default or no passwords; NVD ties this to default administrative password risk in VisiLogic before 9.9.00.
What should utilities do today, with little money: first, remove PLC/HMI management from the public internet — not someday, today. Put remote access behind VPN plus MFA, ideally through a jump host in a small OT DMZ; if MFA/VPN is not available immediately, disable remote access until a supervised window. Second, change all Unitronics default passwords and verify no shared operator/vendor credentials remain. Third, inventory which devices actually control pumps, tanks, lift stations, and chemical feeds, then prioritize those for password changes, firmware/software review, and network isolation. Fourth, enable basic logging where possible: VPN logins, PLC/HMI configuration changes, unusual ladder logic downloads, setpoint changes, alarm suppression, and after-hours sessions. Be careful: any firmware update or segmentation change around live PLC communications must be tested or done in a maintenance window, because breaking control comms can create the same safety event we are trying to prevent.
The line between nuisance access and preparation for physical disruption is intent plus capability. A defaced HMI screen or political message is nuisance-level evidence if there are no process changes, no persistence, and no lateral movement. It becomes preparation for disruption when you see enumeration of PLC tags, repeated logins to engineering interfaces, VisiLogic project upload/download activity, setpoint or alarm threshold changes, new remote-access accounts, scheduled tasks, tunneling tools, or access to historian/SCADA servers that bridge Purdue Level 3 to Level 1/2 control. If the attacker touches pump start/stop logic, tank level thresholds, valve states, chlorine/chemical dosing parameters, or alarm logic, treat it as an operational incident, not just an IT compromise.
My blunt advice: spend the first dollar on removing public exposure and killing default credentials, not on a shiny monitoring platform. Then add low-cost monitoring around the few chokepoints that matter: vendor remote access, engineering workstation access, PLC programming ports, and SCADA-to-field communications. For water utilities, those are the doors between nuisance graffiti and physical consequence.