Why OT security audits are essential in energy
An OT (Operational Technology) security audit is a systematic assessment of industrial infrastructure security — SCADA systems, PLC controllers, RTUs, DCS, and the entire OT network controlling energy processes.
In the energy sector, an OT audit is not just best practice — it is a regulatory requirement. The NIS2 directive obliges critical infrastructure operators to conduct regular security assessments, and the DynoWiper attack in December 2025 showed that inadequately protected OT systems are direct targets of destructive attacks.
OT audits differ fundamentally from IT audits. Industrial systems have different priorities (availability over confidentiality), different constraints (no freedom to patch at will), and different threats (physical process manipulation).
Step 1: Preparation and scope
Define audit objectives. Is the audit for NIS2 compliance, IEC 62443 compliance, or general security posture assessment? Does it cover the entire OT infrastructure or selected systems? Should it include IT/OT segmentation?
Gather input documentation. OT network diagrams (if available), OT asset lists, operational and security procedures, previous audit results and vulnerability scan reports, IT/OT segmentation architecture.
Agree on audit safety rules. Audit timing (maintenance windows for active tests). Prohibited activities list (e.g., active scanning of controllers during production). Escalation procedure if an active threat is discovered. Contact persons on the operator side — OT engineers, dispatchers.
Audit team should consist of an OT cybersecurity expert (lead auditor), industrial networking specialist, vulnerability analyst with OT experience, and an operator representative familiar with the infrastructure.
Step 2: OT asset inventory
The first audit step is a complete OT asset inventory — systems the operator didn’t fully know about are often discovered.
Passive OT network scanning using specialized tools (Nozomi Networks, Claroty, Dragos) that understand industrial protocols and don’t generate traffic that could disrupt processes. Identifying all devices on the OT network — PLC controllers, RTUs, HMI stations, switches, SCADA servers.
Software inventory covers controller firmware versions, engineering workstation operating system versions, SCADA and historian software versions, and installed applications and services.
Criticality classification assigns each asset a criticality level for energy processes. A controller managing a 110kV transformer has different criticality than a temperature sensor in an office building.
Step 3: Network architecture assessment
IT/OT segmentation analysis checks whether physical or logical separation exists between IT and OT networks. Verifying industrial DMZ effectiveness. Identifying undocumented IT↔OT connections (shadow connections). Checking firewall rules at zone boundaries.
OT topology analysis evaluates internal OT network segmentation. Are individual energy substations isolated? Is the Safety zone physically separated from the control network? Is there communication path redundancy?
Remote access assessment verifies remote access mechanisms to OT systems — VPN, jump servers, vendor remote service modules. Is MFA used? Are remote sessions logged and monitored?
Step 4: Vulnerability assessment
Passive vulnerability analysis compares identified firmware and software versions against CVE databases. Identifying known vulnerabilities without active scanning. Prioritization considering exposure and system criticality.
Controller configuration analysis checks whether PLC controllers have unused ports and services disabled. Whether programming mode is password-protected. Whether firmware is current and digitally signed. Whether default passwords have been changed.
Engineering workstation configuration analysis verifies OS hardening, installed security software (AV, EDR), user account and permission configuration, and update and backup policies.
OT protocol analysis assesses whether communication between controllers and HMI stations is authenticated. Whether protocols with security mechanisms are used (OPC UA Secure instead of OPC Classic). Whether OT traffic monitoring exists.
Step 5: Process and procedure assessment
Change management procedures — does every change in OT systems go through a formal approval process? Is there a rollback plan? Are changes documented?
Access management procedures — is there a formal access policy for OT systems? Are accounts reviewed regularly? Do employee departures result in prompt access removal?
Incident response plan — does an OT-specific IR plan exist? Does it address wiperware, ransomware, and process manipulation scenarios? Has it been tested in exercises?
Supply chain management — are OT system vendors assessed for cybersecurity? Is their remote access controlled and monitored?
Backup and recovery — are controller configurations regularly backed up? Are backups stored offline? What is the RTO for critical systems?
Step 6: Penetration testing (optional, during maintenance window)
OT penetration testing requires special care and should only be conducted by experienced OT specialists.
IT/OT segmentation tests attempt to penetrate from IT to OT, simulating APT tactics. Executed from a compromised IT workstation position.
SCADA application tests cover the SCADA server web interface, API, session management, and authentication.
OT protocol tests (in laboratory environment or maintenance window) check whether controllers accept unauthenticated commands and whether OT traffic manipulation is possible.
Step 7: Reporting and remediation plan
Audit report should contain an executive summary for the board, detailed technical findings with criticality classification (CVSS + OT context), discovered vulnerability map on OT network diagram, recommendations list with priorities and cost estimates, and reference to NIS2 and IEC 62443 requirements.
Remediation plan includes quick wins (0-30 days) — changing default passwords, disabling unused services, implementing MFA for remote access. Medium-term (1-6 months) — strengthening segmentation, deploying OT monitoring, firmware updates. Long-term (6-18 months) — full IEC 62443 implementation, building SOC with OT monitoring.
How nFlo conducts OT audits in energy
OT/ICS security audits — full industrial system security audit aligned with IEC 62443 and NIS2 requirements. Team with energy infrastructure experience.
Red Team — advanced IT/OT penetration testing simulating real APT attack scenarios on energy infrastructure.
SOC as a Service — continuous OT security monitoring after audit completion, maintaining achieved security levels.
Schedule a free consultation — we’ll discuss OT security audit scope for your energy company.
Cybersecurity for Your Industry
Learn more about cybersecurity in your industry:
Related topics
See also:
