CISA, Environmental Protection Agency (EPA), National Security Agency (NSA), Federal Bureau of Investigation (FBI), and international partners have released new guidance to help operational technology (OT) owners and operators across critical infrastructure sectors strengthen their cybersecurity defenses. The document outlines a structured approach for creating and maintaining an OT asset inventory and taxonomy, essential tools for identifying and securing critical assets, minimizing cyber risks, and ensuring the continuity of mission-critical services. An OT asset inventory is a regularly updated list of an organization’s systems, hardware, and software, while a taxonomy categorizes these assets by function and criticality to support risk management and incident response. The guidance walks organizations through a detailed process from defining inventory scope and collecting asset data to implementing lifecycle management, and includes recommendations for maintaining and using these inventories to enhance reliability, performance, and cyber resilience. To support practical implementation, CISA also provides conceptual taxonomies developed with input from the energy, oil and gas, and water sectors. For more information, refer to the Foundations for OT Cybersecurity Publication.