FBI & CISA Release Zero Trust Guide for Released Principles

The Federal Bureau of Investigation (FBI) and the Cybersecurity and Infrastructure Security Agency (CISA), joined by the Department of Energy (DOE) and defense partners, have published a joint intelligence document.

Titled “Adapting Zero Trust Principles to Operational Technology,” this guide provides critical infrastructure operators with a strategic roadmap to secure industrial systems against modern cyber threats.

Historically, operational technology (OT) networks relied heavily on strong perimeter defenses.

This created an environment of implicit trust, meaning any user or device inside the network was automatically trusted.

However, as IT and OT systems converge and threat actors increasingly target critical infrastructure, perimeter security is no longer enough.

The new federal guidance strongly urges organizations to adopt an “assume breach” philosophy.

This model operates on the reality that attackers may already be inside the network or will eventually bypass external defenses.

Core Security Pillars for Industrial Systems

By removing implicit trust, security teams can prevent attackers from freely moving laterally across industrial control systems.

The ultimate goal of this shift is to prioritize uninterrupted physical operations, human safety, and equipment reliability.

Implementing Zero Trust in OT requires a defense-in-depth strategy tailored to the physical limits and operational constraints of legacy hardware.

The guidance outlines several key technical priorities:

• Comprehensive Asset Visibility: Security teams cannot protect what they cannot see. Operators must build real-time inventories, classify all connected devices, and establish normal behavioral baselines for both IT and OT environments.
• Identity and Access Management (IAM): The framework mandates continuous validation of both human and machine identities.

It recommends enforcing Multi-Factor Authentication (MFA) where technically feasible and strictly applying least-privilege access, ensuring that users access only what is strictly necessary for their specific roles.

• Network Micro-Segmentation: To contain potential breaches, large flat networks must be divided into smaller, highly controlled zones.

Critical industrial systems must be heavily isolated from less secure enterprise IT networks, utilizing strict communication policies and unidirectional security gateways.

• Continuous Monitoring: Trust is never permanent. Every user and device connection must be continuously authenticated throughout the session, rather than just at initial login.

Organizations should deploy OT-specific threat detection tools that understand industrial protocols to spot dangerous deviations in process parameters.

Alignment with National Frameworks

To ensure consistency across the cybersecurity industry, this guidance aligns with the National Institute of Standards and Technology Cybersecurity Framework (CSF) 2.0 and guidance from the Internet Crime Complaint Center(IC3).

It specifically maps Zero Trust implementation activities to the core NIST functions: Govern, Identify, Protect, Detect, Respond, and Recover.

By carefully planning these security controls, OT operators can successfully bridge the gap between advanced Zero Trust concepts and the physical realities of industrial environments.

This structural approach is designed to prevent cascading physical failures across critical national infrastructure during a cyber incident.

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