'Not a theoretical risk,' feds warn as attackers use AI-made code to hack critical infrastructure controllers

Attackers are using AI-generated exploitation scripts to break into internet-exposed Siemens S7 Series programmable logic controllers (PLCs) at water, manufacturing, energy, and other critical facilities, in what five US federal agencies on Wednesday called an “active threat.”

In this latest round of intrusions against American critical infrastructure, the attackers use open source industrial automation libraries – specifically snap7.dll/python-snap7 – combined with AI coding assistants. Armed with the open source libraries and AI, the miscreants create custom tools that mimic operational technology (OT) monitoring software and provide read/write access to the PLC devices’ memory, configuration data, and ladder logic programs via the S7comm protocol.

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

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While the joint alert from 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) doesn’t attribute the threats to a particular government or criminal group, Iranian cyber operatives are suspected of being behind recent attacks targeting PLCs at water and wastewater facilities across at least 12 states, including a cyberattack that disrupted more than 30 community water systems in Minnesota in late July.

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“This appears to be a continuation of the same suite of activity we suspect is affiliated with Iran targeting PLCs,” Cynthia Kaiser, Halcyon Ransomware Research Center SVP, told The Register. “Iran-affiliated actors and adversaries are actively targeting a wide swath of operational technology because these PLCs underpin essential health, safety, and critical infrastructure across society.”

National security and infosec experts last week told The Register that while there is no indication that the water-system hackers used AI in their intrusions, they worried that attackers would soon add AI to their arsenals for attacks against critical infrastructure. Now, that threat appears to be here.

“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,” Kaiser, a former FBI cyber division deputy assistant director, told us on Wednesday. “The advisory reflects the broader reality that threat actors are using AI to increase their efficiency.”

Siemens S7 Series PLCs under fire

According to the Wednesday security alert, the latest attacks specifically target internet-exposed Siemens S7 Series PLCs across critical manufacturing, energy, water and wastewater, chemical, food and agriculture, and commercial facilities  – in other words: most of the critical industries providing goods and services that Americans use in their daily lives.

“Additionally, Siemens S7 Series PLCs are used in other sectors, including the Defense Industrial Base (DIB), and could be targeted there as well,” the feds warned.

The Register reached out to the agencies for additional information about the attacks but did not receive any response to our questions.

Attackers use internet-scanning services such as Censys and ZoomEye to find exposed, “poorly protected” PLCs running outdated software or using default passwords  – and now they’ve got an AI boost. 

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“Threat actors are using AI assistance to generate exploitation scripts using publicly available information on these Siemens S7 Series PLCs for initial access, credential access, denial of service, and other objectives,” the agencies said. “If these PLCs are exposed to the Internet or insufficiently segmented, then threat actors can exploit various critical and high severity known vulnerabilities in these PLCs.”

The use of AI also indicates “an evolution in threat actor capabilities,” reducing the need for advanced technical knowledge about OT, and allowing the attacker to more rapidly develop working industrial control system malware and attack chains, the alert says.

“I think that the bigger issue is still how exposed OT environments are,” Benny Czarny, CEO and founder of critical infrastructure security firm Opswat, told The Register in an email. “AI makes it much easier for an attacker to create and modify scripts targeting PLCs, so the barrier to attacking industrial systems continues to fall. But for me the answer is not simply better AI detection.”

To mitigate this threat, the feds say critical infrastructure owners and operators should first – immediately – inventory all Siemens S7 Series PLCs in their environment, apply security patches as needed, and make sure no PLCs are accessible from the internet.

It's also worth checking for anomalous S7comm behavior, including connections from non-engineering workstations, unusual data block access patterns, or write operations outside change windows, the feds suggest.

Sequential IP scanning on port 102 and repeated connection attempts with varying parameters can indicate attackers conducting reconnaissance, and Snap7.dll library usage outside approved workstations may also indicate the presence of intruders on the network – so be sure to use these and the rest of the detection strategies detailed in the government security advisory to hunt for anomalies that may indicate a compromise.

In addition to looking for indicators of compromise relevant to these intrusions, Czarny said it's critical to reduce the OT attack surface. 

“If data only needs to leave an OT network, use a data diode,” he said. “There should be no network path back to the PLC for an attacker to exploit. Yes, AI makes this more urgent. But the real lesson for me is still the same: stop giving attackers a path to the critical system in the first place. And do not rely on antivirus and sandboxes to protect your data flow.” ®