Securing Air-Gapped Networks: Lessons from Critical Infrastructure

Air-gapped networks aren't as isolated as you think. Here's what we've learned securing operational technology environments in energy, manufacturing, and transportation sectors.

The Air Gap Myth

Many organizations believe physical isolation equals security. In reality:

• USB drives bridge the gap daily
• Maintenance laptops move between networks
• Vendors require remote access for support
• Data diodes have configuration weaknesses

Real-World Attack Vectors

Vector 1: Supply Chain Compromise

Malware can enter through:

• Infected firmware updates
• Compromised vendor software
• Malicious USB drives from suppliers

Vector 2: Insider Threats

Whether malicious or accidental:

• Engineers copying files between networks
• Unauthorized wireless access points
• Personal devices on OT networks

Vector 3: Maintenance Windows

The most vulnerable time:

• Vendor remote access sessions
• Software update installations
• Configuration changes

Defense-in-Depth Strategies

Layer 1: Physical Controls

• Strict USB device policies
• Network segmentation with data diodes
• Physical access monitoring

Layer 2: Network Monitoring

Even air-gapped networks need monitoring:

• Deploy OT-specific IDS/IPS
• Monitor for anomalous traffic patterns
• Log all cross-boundary data transfers

Layer 3: Endpoint Hardening

• Application whitelisting
• Disable unnecessary services
• Regular integrity checking

Key Takeaways

Air gaps provide a layer of defense, but shouldn't be your only control. Build defense-in-depth assuming the gap will be bridged. Need help securing your OT environment? Our ICS/SCADA security assessments identify vulnerabilities before attackers do.