CISA’s Guide to OT Network Segmentation

🛡️Why Network Segmentation Matters

Network segmentation is a cornerstone of OT cybersecurity. It involves dividing a network into isolated, secure zones—either physically or virtually—each acting as a self-contained subnetwork. This approach:

• Reduces risk
• Enhances control
• Prevents lateral movement in the event of a breach

The Cybersecurity and Infrastructure Security Agency (CISA) emphasizes the importance of segmentation and provides a clear, actionable framework for its implementation—especially for critical infrastructure environments.

Top 5 Benefits of Network Segmentation

1. Threat Containment: Compromised systems are confined within their segment, preventing wider disruption.
2. Smaller Attack Surface: Limiting inter-zone communication reduces paths for attackers to reach sensitive assets.
3. Protection of Critical Assets: High-value systems like DCSs, PLCs, HMIs, and control servers are isolated from less secure IT zones.
4. Improved Monitoring: Smaller zones allow for more precise anomaly detection and event tracking.
5. Compliance Enablement: Helps meet requirements in frameworks like ISA/IEC 62443, which mandate segmentation as a baseline control.

Key Components of an Effective Segmentation Strategy

1. Define and Group Zones

Organize assets by function and risk level. Typical OT zones include:

• Control Zone: PLCs, DCS, SCADA, most critical layer.
• Historian Zone: Operational data aggregation.
• MES Zone: Operational-to-enterprise handoff.
• Remote Access Zone: For secure third-party or vendor access.
• Enterprise IT Zone: Business apps and office systems.

2. Establish Secure Conduits Between Zones

• Strict Communication Rules: Permit only essential traffic between zones, with defined protocols and endpoints.
• Firewalls with ACLs: Use industrial firewalls and Access Control Lists to strictly manage inter-zone traffic.
• DMZ Deployment: A DMZ acts as a secure proxy zone between IT and OT, preventing direct access while enabling controlled data exchange.

3. Test, Monitor, and Maintain Continuously

• Validate Controls: Post-deployment testing ensures segmentation functions correctly without disrupting operations.
• Continuous Monitoring: Track traffic flows and flag deviations or unauthorized access attempts.
• Ongoing Review: Update policies as new assets or threats arise.

🏆 The Champion Advantage

Effective segmentation requires more than IT knowledge, it demands a deep understanding of industrial processes. That’s where Champion Technology Services excels.

We deliver segmentation strategies that:

• Protect operations without disrupting uptime
• Align with CISA guidance and industry specific standards
• Bridge IT security best practices with OT realities

We combine cybersecurity leadership with control system expertise to design and implement resilient, scalable, and compliant network architectures for critical infrastructure environments.