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.

Follow me on Twitter: @securityaffairs and Facebook and Mastodon

Pierluigi Paganini

(SecurityAffairs – hacking, Water Utilities)

NSA, CISA, FBI, DOE, and EPA warn of active AI-assisted attacks against Siemens S7 PLCs across US critical infrastructure sectors.

Five U.S. federal agencies issued a joint advisory this week warning of an active hacking campaign against Siemens S7 Series programmable logic controllers. The advisory, CISA AA26-231A, is co-signed by NSA, FBI, DOE, and EPA and covers every S7 generation, from the S7-200 to the S7-1500 F-series safety controllers.

The advisory is direct about one thing from the first paragraph: this is not a theoretical risk.

“The threat actors are conducting reconnaissance and capability development against U.S.-based Siemens PLC installations using AI-generated exploitation scripts disguised as legitimate monitoring tools. The actors leverage Internet scanning services to find Internet-exposed PLCs running outdated software or that are otherwise poorly protected.” reads the advisory. “The U.S. critical infrastructure sectors most targeted by this threat activity include Critical Manufacturing, Energy, Water and Wastewater, Chemical, Food and Agriculture, and Commercial Facilities. This is not a theoretical risk—it is an active threat. “

The key detail is how the attackers try to hide their activity. They make their scripts look like legitimate OT monitoring software, making it harder for security teams to notice them while they map the target environment.

The tools themselves are not custom malware. The attackers use the open-source snap7.dll and python-snap7 libraries, which are legitimate industrial automation tools. These libraries can communicate directly with Siemens PLCs over S7comm on TCP port 102, allowing access to PLC memory, configuration data and ladder logic programs.

“Using AI to generate exploitation scripts represents an evolution in threat actor capabilities, dramatically reducing the technical expertise and time required to develop working ICS exploitation scripts and malicious tools. In addition, AI enables adversaries to rapidly leverage additional attack vectors and adapt to defensive measures.” continues the advisory. “Threat actors can easily collect public information about vulnerabilities and weaknesses, find exposed and exploitable PLCs, and use AI-generated scripts to act on that information. If PLCs are exposed to the Internet, they are at high risk for exploitation.”

Researchers warn that a defender who patches a vulnerability may now find the attacker’s tooling already adapted before the change window closes.

The observed activity breaks into two phases. Actors use scanning services like Censys and ZoomEye to locate Internet-exposed PLCs, then run read operations to understand the target environment before any writes happen. The authoring agencies assess this as pre-positioning: the actors are building a map and testing their techniques against specific CPU models, refining as they go, before they’re ready to cause disruption.

The target list covers Critical Manufacturing, Energy, Water and Wastewater, Chemical, Food and Agriculture, and Commercial Facilities. The Defense Industrial Base is also named, given its use of S7-series hardware. If these actors move from read to write, the potential consequences include process disruption, equipment damage, and safety incidents through manipulation of interlocks or emergency shutdown systems, and cascading effects across interconnected supply chains.

The advisory flags third-party exposure as a specific problem. Asset owners who rely on system integrators or managed service providers for remote PLC access may not know their controllers are reachable from the Internet. If an external support partner holds credentials for your S7 devices and you haven’t recently verified that those connections are segmented and monitored, this advisory is a good prompt to check.

There are several clear signs defenders can monitor. They should look for S7comm connections from devices that are not normally used for engineering, PLC read or write activity outside scheduled maintenance, and scans of multiple IP addresses on TCP port 102. It is also worth checking for Python processes loading snap7.dll on systems where it should not be present. Connections from unexpected countries or locations should also raise an alert.

On the mitigation side, the agencies prioritize inventory first, then patching with Internet-facing controllers at the top of the queue. Block TCP port 102 at the perimeter firewall, require password protection on all controllers, configure protection levels to limit what an unauthenticated or low-privilege session can read or write, and deploy ICS-aware monitoring capable of baselining legitimate S7comm behavior. Disabling the PLC web server where it’s not needed and limiting simultaneous S7comm sessions also appear in the guidance, alongside TIA Portal’s know-how protection and complete restart protection features.

The advisory closes by recommending direct engagement with Siemens ProductCERT for model-specific hardening and patch compatibility verification, which matters in OT environments where a firmware update can interact badly with third-party integrations and can’t simply be rolled back.

Follow me on Twitter: @securityaffairs and Facebook and Mastodon

Pierluigi Paganini

(SecurityAffairs – hacking, CISA)

CISA and the NSA warn of an active Siemens PLC cyber threat using AI-generated exploit scripts disguised as monitoring tools. Protect your OT now.

Related Posts:

• Jewelbug APT Group Operations Combine Espionage and Fraud
• Cisco Talos Discovers JWR Phishing Framework
• PATCHCORD Malware Hits Afghan Telecom in New APT36 Campaign

The post US Agencies Warn of AI-Generated Exploits Targeting Siemens S7 PLCs appeared first on Daily CyberSecurity.

After attacks hit 30+ Minnesota water systems, CISA urged utilities to remove internet-exposed PLCs and strengthen OT security.

Between Sunday and Monday, July 26 and 27, a coordinated cyberattack hit operational technology (OT) systems at more than 30 community water utilities across the state, according to Minnesota IT Services (MNIT).

“A coordinated cyberattack targeted operational technology at more than 30 Minnesota community water systems on July 26 and 27. Minnesota IT Services (MNIT) immediately activated the state’s cybersecurity incident response capabilities.” reads the statement published by MNIT. “MNIT continues to collaborate with federal, state, local, Tribal, and private-sector partners to investigate the attack, support affected communities, and strengthen the security of Minnesota’s critical infrastructure.”

The agency activated its statewide incident response the moment it learned of the attack, and it’s still active as of this week.

Four cities went public with details: Braham, Maple Plain, Plymouth, and South St. Paul. Braham took the hardest hit of the group; the town of about 1,700 people had its water plant knocked offline entirely after attackers disabled the computerized controls running its well and treatment systems.

State and federal investigators are working to determine attribution, but the timing is hard to ignore: the attacks came four days after CISA updated its advisory on Iranian-affiliated actors targeting programmable logic controllers across US critical infrastructure. No formal attribution has been made, but Tenable researchers assess the operational pattern is consistent with CyberAv3ngers, an Iran-linked group formally tied to the IRGC.

“Federal and state officials have not publicly attributed the Minnesota attacks to any specific actor. However, the operational pattern is consistent with the CyberAv3ngers threat ecosystem, a state-directed group the U.S. government has formally attributed to Iran’s Islamic Revolutionary Guard Corps Cyber-Electronic Command.” reported Tenable.

CISA now warns of a surge in attacks targeting internet-exposed PLCs at water utilities. Attackers have changed passwords and IP addresses to lock out operators, causing boil water notices and forcing some facilities to switch to manual operations. The US agency urges organizations to remove publicly accessible PLCs and other OT systems from the internet immediately.

“CISA is currently observing a significant increase in cyber threat actors targeting programmable logic controllers (PLCs) in the Water and Wastewater Systems (WWS) Sector. CISA urges critical infrastructure owners, operators, and integrators to remove publicly exposed PLCs and other operational technology (OT) from the internet as soon as possible.” reads CISA’s alert. “Threat actors targeting exposed PLCs have modified passwords to lock out operators and disconnected the PLCs by changing their IP addresses. This activity has resulted in boil water notices and sustained manual operations.”

The FBI confirmed that utility companies in at least seven states have reported PLC-related incidents. The attacks aren’t sophisticated in the traditional sense, after remotely accessing internet-facing devices, the actors changed IP addresses and passwords, resulting in loss of monitoring and control functionality. That’s it. Default or weak credentials on internet-exposed hardware, and suddenly operators are locked out of their own systems.

CVE-2021-22681 is a critical Rockwell Automation vulnerability (CVSS 9.8) that remained unexploited for years because industrial control systems are difficult to patch without disrupting essential services. Since March 2026, however, Iranian-affiliated threat actors have actively exploited the flaw, prompting CISA to add it to its Known Exploited Vulnerabilities catalog. Rockwell has confirmed that no security patch is available, making network isolation and other compensating controls essential.

That last sentence is worth sitting with. A CVSS 9.8 vulnerability in controllers that run public water infrastructure, no patch, actively exploited. The compensating control is network isolation, which is exactly what CISA is now urgently requesting.

“These threat actors are targeting water entities of all sizes. Even water organizations with mature cybersecurity processes should validate their external connections, as this targeting activity includes cellular modems installed by operators, vendors, or system integrators that may not be documented or included in routine attack surface scans.” continues the alert. “OT assets exposed to the internet have an increased risk of defacement, configuration changes, operational disruptions, and, in severe cases, physical damage.”

A July 2026 update to CISA’s advisory found that attacks exploiting internet-exposed PLCs have expanded beyond Rockwell Automation to include Schneider Electric and Siemens devices. The advisory also documents attackers stealing PLC project files for the first time and adds new guidance to detect tampering with reusable code modules embedded in industrial control programs.

Exfiltrating project files means the attacker is taking the engineering logic of the plant, the actual programmed behavior of the industrial process, and studying it offline. That’s reconnaissance for a more targeted future attack, not just disruption for its own sake.

The Minnesota attacks resulted in boil water notices and sustained manual operations at affected utilities. Drinking water remained safe in most cases, and contingency procedures held. But the affected cities include Maple Plain, Braham, South St. Paul, and Plymouthm not isolated rural facilities, but communities of real scale. CyberAv3ngers is known for targeting small water and municipal facilities, which experts believe are among the lowest-hanging fruit in US critical infrastructure. Many small and rural facilities lack dedicated cybersecurity resources. That’s the point. These attacks aren’t about technical sophistication. They’re about finding the organizations with the least capacity to defend themselves and demonstrating that the capability to disrupt public services exists and can be exercised.

CISA’s alert specifically notes that even mature organizations should validate their external connections, because the targeting includes cellular modems installed by operators, vendors, or system integrators that may not appear in routine network scans. A modem installed by a contractor for remote access and never documented in the asset inventory is still an attack surface. The practical checklist is short: get PLCs off the internet, segment OT networks from IT networks, change default credentials, and audit every remote access path, including the ones you didn’t authorize.

“CISA recommends organizations implement the following mitigations:

• Disconnect the PLC from the internet. Remote access for operational purposes should go through a VPN or gateway device, not directly to the PLC.
• Enable password protection and change default passwords.
• Allowlist IPs to only allow remote access from known engineering laptops or other critical OT assets.

After disconnecting PLCs from the internet, operators should ensure they have a known clean backup of the PLC image in case they are locked out by a modified password.” concludes CISA. Note: Owners, operators, and integrators of Rockwell Automation MicroLogix 1400 PLCs should see Rockwell Automation’s IMPORTANT NOTICE: Restoring Access to a MicroLogix 1400 Controller When the Password Is Unknown for guidance addressing this activity.”

Follow me on Twitter: @securityaffairs and Facebook and Mastodon

Pierluigi Paganini

(SecurityAffairs – hacking, CISA)