Feds Warn of AI-Generated Code Threat to Critical Infrastructure Controllers

"This is not a theoretical risk – it is an active threat," the feds warned.

Five federal agencies issue a joint alert

The National Security Agency (NSA), Cybersecurity and Infrastructure Security Agency (CISA), Federal Bureau of Investigation (FBI), Department of Energy (DOE), and Environmental Protection Agency (EPA) issued a joint security advisory describing active intrusions against internet‑exposed Siemens S7 Series programmable logic controllers (PLCs). The agencies said attackers are exploiting those devices at water, manufacturing, energy, chemical, food and agriculture, and commercial facilities — and noted the devices are also used in the Defense Industrial Base (DIB).

AI plus snap7.dll/python‑snap7: a new attack pattern

According to the advisory, attackers combine open source industrial automation libraries — specifically snap7.dll and python‑snap7 — with AI coding assistants to generate exploitation scripts. Using publicly available information about Siemens S7 Series PLCs and an AI boost, miscreants are creating custom tools that mimic operational‑technology monitoring software and that provide read/write access to PLC memory, configuration data, and ladder logic via the S7comm protocol.

The alert warns this evolution reduces the need for advanced OT knowledge and speeds development of industrial control system malware and attack chains. As Halcyon Ransomware Research Center SVP Cynthia Kaiser put it to The Register, “What the advisory highlights with regard to AI usage aligns with what we’ve expected: state‑sponsored adversaries are leveraging AI across the board for discrete tasks, like code checks and scripting, to scale their operations and move faster.”

How attackers find and exploit exposed PLCs

The agencies said attackers are using internet‑scanning services such as Censys and ZoomEye to locate exposed, “poorly protected” PLCs running outdated software or using default passwords. The advisory calls out specific tactics and objectives: initial access, credential access, denial of service, and other goals achieved by exploiting critical and high‑severity known vulnerabilities in these PLCs when they are exposed to the internet or insufficiently segmented.

The Register also reported investigators suspect Iranian cyber operatives are behind recent PLC attacks at water and wastewater facilities across at least 12 states, including a cyberattack in late July that disrupted more than 30 community water systems in Minnesota. The joint advisory itself does not attribute the activity to a named government or criminal group.

Detection signals and immediate mitigations the feds recommend

The government advisory lays out practical detection and mitigation steps. Owners and operators are urged to immediately inventory all Siemens S7 Series PLCs, apply security patches where required, and ensure no PLCs are accessible from the internet. The advisory lists anomalous S7comm behavior to hunt for, including:

• connections from non‑engineering workstations;
• unusual data block access patterns;
• write operations outside approved change windows;
• sequential IP scanning on port 102 and repeated connection attempts with varying parameters, which can indicate reconnaissance; and
• Snap7.dll library usage outside approved engineering workstations as a potential sign of intruders.

Beyond detection, critical infrastructure security CEO Benny Czarny told The Register the attack surface must be reduced. He recommended using one‑way data diodes where OT data needs to leave a network and ensuring no network path back to the PLC exists. “There should be no network path back to the PLC for an attacker to exploit,” Czarny wrote. He added that while AI heightens urgency, the underlying lesson remains: stop giving attackers a path to critical systems, rather than relying solely on antivirus and sandboxes.

What this means for technologists, policymakers, and water utilities

Technologists and security teams: Perform immediate inventories of Siemens S7 Series PLCs, patch devices, and hunt for the S7comm anomalies and Snap7.dll usage flagged in the advisory. Tighten segmentation and remove internet access to PLCs.

Policymakers and regulators: The advisory underscores a cross‑agency concern about internet‑exposed OT and the way AI tools can lower technical barriers; the agencies’ joint notice is a signal that federal guidance on OT segmentation and exposure will remain a priority.

Water and wastewater operators: Operators should check for the reconnaissance signatures the advisory names and verify that no PLCs are directly reachable from the internet. The Register noted recent water‑system intrusions across at least 12 states and an incident that disrupted more than 30 Minnesota community water systems in late July, reinforcing the immediate stakes.

The joint message from the NSA, CISA, FBI, DOE and EPA is unambiguous: attackers are combining open source PLC libraries and AI to accelerate exploitation, and the first line of defense is inventory, patching and removing internet exposure. The advisory offers a short list of concrete technical signals to hunt for — sequential scans on port 102, unusual S7comm access patterns, and unauthorized Snap7.dll usage — and a clear operational imperative: deny attackers any network path back to PLCs.

Read the original advisory and coverage at The Register: https://www.theregister.com/security/2026/08/19/not_a_theoretical_risk_feds_warn_as_attackers_use_ai_made_code_to_hack_critical_infrastructure_controllers/5289960