Secure Connectivity Principles for Operational Technology (OT) | CISA

The Cybersecurity and Infrastructure Security Agency (CISA) has published new security guidelines specifically addressing connectivity risks in operational technology (OT) environments. This comes as industrial control systems face escalating threats from ransomware groups and state-sponsored actors targeting critical infrastructure like power grids, manufacturing plants, and water treatment facilities.

OT systems—which manage physical processes through industrial control systems (ICS), SCADA systems, and programmable logic controllers (PLCs)—historically operated in isolated networks. Modern digital transformation initiatives now connect these systems to corporate IT networks and cloud services, creating new attack surfaces. John Riggi, National Advisor for Cybersecurity at the American Hospital Association, notes: "The convergence of IT and OT networks means vulnerabilities in office software can become pathways to disrupt life-safety systems. We've seen this in healthcare where attacks on IT systems forced hospitals to suspend critical care operations."

CISA's principles emphasize segmentation, encrypted communications, and continuous monitoring:

1. Defensible Architecture: Implement network segmentation between OT, IT, and cloud environments using firewalls and industrial DMZs. Micro-segmentation within OT zones limits lateral movement.
2. Encrypted Communications: Mandate TLS 1.3 or IPsec for all remote connections. Replace legacy protocols like HTTP and FTP with secure alternatives.
3. Asset Visibility: Maintain real-time inventories using tools like CISA's Cyber Hygiene services to detect unauthorized devices.
4. Least Privilege Access: Enforce role-based access controls and multi-factor authentication for OT engineers and third-party vendors.
5. Continuous Monitoring: Deploy network detection tools tuned for OT protocols like Modbus and DNP3 to identify anomalies.

Practical implementation steps include conducting network topology mapping, disabling unused ports on PLCs, and establishing encrypted VPN tunnels for remote maintenance. Organizations should prioritize patching critical systems using CISA's ICS Patch Tuesday guidance and validate configurations against the Cybersecurity Performance Goals. As industrial ransomware attacks increased 87% in 2023 per Dragos, these principles provide actionable frameworks for securing converged environments without compromising operational continuity.