Attackers no longer need to know how to write an exploit for a Siemens controller. AI will do it for them.
That is the message from the National Security Agency and four other U.S. agencies, which warned Aug. 19 that threat actors are using AI-generated scripts against internet-exposed Siemens S7 programmable logic controllers (PLCs) — the industrial computers that run machinery and processes in factories, power systems and water plants.
The joint cybersecurity advisory describes an active threat to U.S.-based installations and says critical manufacturing, energy and water and wastewater are among the sectors most targeted.
The mechanics of AI-assisted exploitation
The scripts are aimed at the S7-200, S7-300, S7-400, S7-1200 and S7-1500 families, including F-series safety controllers. Threat actors are combining the open-source snap7.dll/python-snap7 industrial automation library with AI-assisted scripting to build tools that mimic legitimate monitoring software. Those tools provide read and write access to PLC memory, configuration data and ladder logic through the S7comm protocol.
None of this required a novel vulnerability, just a library anyone can download and a model to write the glue code. The agencies say AI is “dramatically reducing the technical expertise and time required” to develop working industrial control system exploitation tools, and that the actors are reading now so they can write later: using read access to map target environments in preparation for future write operations that could disrupt physical processes.
Part of a broader operational technology threat
The federal agencies say the Siemens activity is one part of a wider PLC threat. An April joint advisory attributed attacks on internet-connected operational technology, including Rockwell Automation/Allen-Bradley PLCs, to Iranian-affiliated actors. The Siemens advisory does not attribute the new activity to Iran or another actor.
Internet exposure has also appeared in attacks on other operational technology. In June, the National Security Agency (NSA), Cybersecurity and Infrastructure Security Agency (CISA) and other federal partners warned that unattributed actors were compromising internet-exposed automatic tank gauge systems used in the energy, chemical and transportation sectors, as well as food and agriculture. The actors subsequently modified the systems through command execution, according to the agencies.
Physical impacts seen in the water sector
The operational consequences became clearer in the water sector in July.
A Federal Bureau of Investigation and Environmental Protection Agency alert said utilities in at least seven states had reported attacks on internet-facing Rockwell MicroLogix 1100 and 1400 PLCs. Operational effects reported to the FBI have included loss of pressure and flooding. Investigators also found similarities in third-party-supplied network setups across several victims, which they said could allow attackers to repeat successful access methods across customers.
Third-party risks and mitigation strategies
The Siemens advisory raises a similar third-party risk. It says system integrators or managed service providers may have remote PLC access without asset owners realizing their systems are exposed, and tells organizations using those providers to ask them to implement the recommended controls.
Those controls include inventorying S7 controllers, checking firmware, removing internet exposure, blocking S7comm traffic on TCP port 102 at perimeter firewalls and requiring multifactor authentication for remote access to operational technology networks. The agencies also recommend monitoring for connections from non-engineering workstations, sequential scanning and write operations outside approved change windows.
Siemens updates security guidance
Siemens, for its part, is not sounding the same alarm. “At this point in time, we have not identified increased attack levels or unknown vulnerabilities in Siemens ICS products,” a company spokesperson told Cybersecurity Dive.
The company updated its ProductCERT security bulletin on Aug. 21 to reference the new advisory. It recommends current software versions, removing devices from inadequately secured networks or adding protections such as firewalls and using strong, unique passwords. The federal advisory sets no remediation deadline and asks U.S. organizations to report suspicious activity to CISA or the FBI.