On August 19, 2026, the National Security Agency (NSA), the Cybersecurity and Infrastructure Security Agency (CISA), the Federal Bureau of Investigation (FBI), the Department of Energy (DOE) and the Environmental Protection Agency (EPA) released a joint Cybersecurity Advisory (AA26-231A) warning that threat actors are actively targeting Siemens S7 Series programmable logic controllers (PLCs) that are exposed to the internet or insufficiently segmented from it. The activity spans the S7-200, S7-300, S7-400, S7-1200 and S7-1500 series and most heavily affects the Critical Manufacturing, Energy, Water and Wastewater, Chemical, Food and Agriculture and Commercial Facilities sectors, with potential exposure in the Defense Industrial Base as well.

According to the authoring agencies, threat actors are using AI-generated exploitation scripts, disguised as legitimate operational technology (OT) monitoring tools, to conduct reconnaissance and build capability against exposed PLCs. The Tenable Research Special Operations Team (RSO) has put together a frequently asked questions (FAQ) blog to help security and OT teams understand the threats, the techniques involved and the mitigations offered by the authoring agencies. The advisory itself notes that ongoing PLC targeting is broader than Siemens alone and that all PLC owners and operators, regardless of vendor, should apply all relevant mitigations.

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