CISA Warns Water Utilities: Find Your Exposed PLCs Before Attackers Do
CISA Warns Water Utilities: Find Your Exposed PLCs Before Attackers Do
August 27, 2026 
CISA urges water utilities to find and secure internet-exposed PLCs after July attacks showed how easily exposed industrial systems can be compromised.
Over 100 internet-exposed systems in the US water and wastewater sector got hit by cyberattacks in July 2026, and CISA’s response wasn’t just an incident report, it was a how-to guide for making sure it doesn’t happen to you next. The agency’s exposure reduction guidance, published August 21, walks through exactly how organizations can find their own internet-facing weak points before an attacker does.
The pattern behind the July attacks was surprisingly simple. Most of the affected systems were programmable logic controllers (PLCs), small industrial computers that control pumps and valves. Many connected directly to cellular modems and had no firewall or gateway between them and the internet. CISA warns that this type of setup can expose PLCs to serious security risks.
“Directly connecting PLCs to the internet through cellular modems can create significant security risks. However, internet exposure reduction does not mean disabling necessary remote access; organizations should remove remote access when it is unnecessary and secure it when it is necessary.” states CISA.
Hackers remotely accessed exposed PLCs, changed device IP addresses and passwords, and in some cases disabled shutdown processes and alarms, creating what CISA called unsafe conditions without notifying the operators running the actual equipment. Iran is the suspected actor behind much of this activity, likely tied to the ongoing war involving the US and Israel, though officials have stopped short of a formal attribution.
CISA presents reconnaissance as an ongoing process. Organizations need to know which systems they expose to the internet and can use tools such as Shodan, Censys, or CISA’s Cyber Hygiene Vulnerability Scanning service to check their own IP ranges from the outside.
The review should also cover ports used by industrial systems. Besides SSH, RDP, and HTTP, CISA highlights protocols such as Modbus, EtherNet/IP, DNP3, BACnet, and OPC UA. Finding one of these ports open does not automatically mean the system has been compromised, but it does indicate an exposure that needs to be investigated and addressed quickly.
Where remote access is genuinely necessary, CISA’s advice is to route everything through a secure, centrally managed gateway rather than connecting straight to a PLC, HMI, or remote terminal unit. Pair that with phishing-resistant multi-factor authentication, unique credentials instead of shared defaults, and active monitoring of traffic in and out, and you’ve closed most of the gap that let this particular wave of attacks succeed in the first place. None of this is exotic security engineering; it’s the same basic hygiene that’s been recommended for years, just finally getting attention because attackers are actually using the gap.
This isn’t an isolated incident CISA is responding to reactively, either. The water sector attacks sit inside a much larger pattern of nation-state interest in US and allied critical infrastructure, from China’s Volt Typhoon reportedly pre-positioning malware inside American infrastructure as a potential wartime disruption tool, to Russian-linked campaigns testing water and energy systems across Europe as part of broader pressure on NATO. If a foreign government is willing to spend years quietly waiting inside a power grid, an exposed PLC with a factory-default password isn’t a minor oversight, it’s an open invitation.
“CISA urges all critical infrastructure organizations to route all necessary remote access through a secure gateway, firewall, VPN, or other centrally managed access solution, rather than connecting directly to a PLC, human-machine interface (HMI), or remote terminal unit (RTU).” concludes CISA. “The July 2026 malicious cyber activity targeting WWS Sector entities demonstrates the consequences of directly exposing PLCs to the internet. Threat actors remotely accessed internet-exposed PLCs, changed device IP addresses and passwords, and caused loss of monitoring and control functionality and, in some cases, operational disruptions.”
If you run anything with the letters PLC, SCADA, ICS, or HMI in its job description, this guidance isn’t optional reading for next quarter. Go run the scan today, because the alternative is finding out the hard way that someone else already ran it for you.
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(SecurityAffairs – hacking, Water Utilities)
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