US warns of Siemens PLC hacking threat

Several US government agencies, including the United States — National Security Agency, FBI, Department of Energy, Environmental Protection Agency, and United States — Cybersecurity and Infrastructure Security Agency, issued a joint cybersecurity advisory on August 19, 2026, warning of an 'active threat' to all Siemens S7 Series programmable logic controllers (PLCs) used across critical infrastructure sectors such as manufacturing, energy, water and wastewater, chemical, and food and agriculture. The advisory states that unidentified hackers are attempting to breach these devices, potentially causing disruption of critical processes, safety incidents, downtime, equipment damage, data compromise, and cascading impacts. The warning comes amid a series of cyber incidents targeting local water systems in multiple states, which cybersecurity experts suspect are linked to Iran, though federal officials have not formally linked Iran to the recent attacks. The advisory also notes that hackers are using AI to lower the technical barrier for developing exploits. Siemens did not immediately respond to a request for comment. This advisory follows earlier warnings from CISA about increased targeting of PLCs, including a July 22 advisory about Iranian-affiliated hackers exploiting devices from Siemens, Rockwell Automation, and Schneider Electric.