How to Conduct a Risk Assessment on Industrial Networks
Industrial networks have unique constraints—real-time operations, safety considerations, legacy equipment, and limited patching windows—so their risk assessments differ from IT environments. Use the following structured approach.
1. Define Scope and Objectives
Start by clarifying what you are assessing.
Tasks
Identify systems: PLCs, RTUs, HMIs, historian servers, SCADA, safety instrumented systems, field devices.
Map network zones and conduits (e.g., ICS zones, DMZ, enterprise zone).
Define assessment objectives (safety, uptime, regulatory compliance, availability, integrity).
Tips
Keep scope manageable—focus on high-value areas first (e.g., production lines, power systems).
Include both cyber and operational risks.
2. Collect Asset Information
You cannot protect what you don’t know.
Tasks
Build an asset inventory:
Hardware (PLCs, switches, engineering workstations, VFDs)
Software/firmware versions
Communication protocols (Modbus, EtherNet/IP, Profinet)
Network diagrams/topology
Identify critical assets essential for safety or production.
Tools Commonly Used
Passive network monitoring (Nozomi, Claroty, Dragos)
Configuration audits
Interviews with control engineers / operators
3. Identify Threats
Define what could harm the network.
Typical Threat Categories
Cyber threats: ransomware attacks, remote exploitation, malware, phishing of engineering staff.
Operational threats: human error, misconfiguration, incorrect firmware updates.
Physical threats: unauthorized access to cabinets, theft of devices.
Environmental threats: power failures, heat, electromagnetic interference.
4. Identify Vulnerabilities
Determine weaknesses that threats could exploit.
Common ICS/OT Vulnerabilities
Legacy systems with no patching
Default or shared passwords on PLCs
Flat networks without segmentation
No logging or monitoring
Unsupported operating systems (WinXP, Win7)
Insecure protocols (Modbus TCP, DNP3)
Use vulnerability scans very carefully—prefer OT-safe tools or passive discovery.
5. Determine Likelihood and Impact
Risk = Likelihood × Impact
But in OT, impact often matters more (safety > finance > downtime > data loss).
Impact Dimensions
Human safety
Environmental harm
Production downtime and financial loss
Equipment damage
Regulatory non-compliance
Likelihood Considerations
Does the system face the internet?
Are remote vendor connections enabled?
Is the network segmented?
Known vulnerabilities in the devices?
Strength of existing controls?
Use a qualitative scale (Low/Med/High) or quantitative scoring if required.
6. Calculate Risk Level
Use a risk matrix or scoring method to classify each risk.
Example
Threat Vulnerability Likelihood Impact Risk Level
Ransomware entering via remote access Single-factor authentication Medium High High
Unauthorized PLC programming Unlocked control cabinet Low Very High High
Production data loss Outdated HMI OS Medium Medium Medium
7. Prioritize Risks
Sort risks by:
Safety-critical first
Production-critical
High likelihood exploitation paths
Vulnerabilities with easy remediation
This helps allocate budget and engineering resources.
8. Recommend Mitigation Measures
Focus on feasible OT-friendly controls.
Common Controls
Network segmentation: Implement ICS zones/DMZs, restrict conduits.
Access control: MFA for remote access, unique accounts for engineers.
Monitoring & detection: Passive network IDS/ICS anomaly detection.
Patch and configuration management: Controlled patching schedules, vendor-approved firmware updates.
Backup & recovery: Offline backups for PLC programs, SCADA configurations.
Hardening devices: Disable unused services, set strong passwords.
Physical security: Lock cabinets, badge controls, CCTV.
Procedural controls: Change management, role-based access, training.
9. Document the Entire Process
Your report should include:
Scope and objectives
Asset inventory summary
Threat and vulnerability findings
Risk matrix and prioritization
Mitigation recommendations
Residual risk after remediation
Executive summary for management
Documentation is essential for regulatory audits and budget justification.
10. Review and Reassess Periodically
Industrial environments change slowly, but risks evolve quickly. Perform reassessments:
After major upgrades
After a security incident
At least annually for critical systems
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