Practical OT cybersecurity for manufacturing, aerospace and defence environments
Operational technology (OT) manages physical processes, production equipment and, in some environments, safety functions. Security measures must therefore reduce cyber risk without introducing unacceptable operational or safety risk. The objective is not to copy office-IT controls onto the plant floor, but to adapt them to the realities of uptime, reliability, legacy equipment and controlled change.
IT practices do not transfer directly
Rapid patching, active vulnerability scanning, endpoint agents, and frequent reboots are common in IT environments. However, in OT environments, these actions can disrupt deterministic communications, invalidate vendor support, compromise safety logic, or halt production. All security changes should be risk-assessed, tested in a representative environment, when possible, approved through management of change, and scheduled in coordination with operations, engineering, and equipment vendors.
Start with a definitive view of the environment
A reliable OT security program begins with a current inventory and architecture record. Identify controllers, HMIs, engineering workstations, servers, network devices, software and firmware versions, remote connections, data flows, owners, criticality and support status. Passive network monitoring is often the safest initial discovery method because it observes existing traffic rather than interrogating fragile devices; however, sensor deployment should still be planned and validated with plant personnel.
Key point
Asset inventory is not a one-time exercise. It must be updated through installations, removals, configuration changes and the full asset lifecycle.
Segment before and during patching
Network segmentation is an essential compensating control when immediate patching is not possible, but it does not replace vulnerability management. Separate enterprise IT from OT, implement an industrial demilitarized zone as needed, restrict communications between zones and conduits, enforce deny-by-default rules, control vendor access, and isolate unsupported assets. Prioritize patches and firmware updates based on risk, test them, ensure rollback plans are in place, and deploy during approved maintenance windows.
Governance must include the plant floor
OT security is not solely IT’s responsibility. Effective governance distributes responsibilities across operations, engineering, maintenance, safety, cybersecurity, and third-party suppliers. It also defines technology owners, approved remote-access paths, change-control requirements, exception management, and documented compensating controls. Decisions should be evaluated based on safety, availability, process integrity, and recovery objectives, rather than only the number of vulnerabilities addressed.
Prepare for incidents without creating one
OT incident response plans must address potential physical consequences. They should specify who is authorized to isolate equipment, criteria for resuming production, requirements for safe shutdown, procedures for maintaining manual operations, and when to involve vendors, safety teams, legal counsel, or regulators. Tabletop exercises should simulate realistic scenarios with operations and engineering teams, focusing on containment, recovery from trusted backups, and capturing lessons learned.
A practical path forward
Securing OT while minimizing production disruption relies on five key disciplines:
- accurate visibility,
- risk-based segmentation,
- controlled maintenance,
- shared governance and
- rehearsed response.
The goal is not to eliminate all operational impact, but to enable better-informed changes, enhance resilience, and reduce unexpected issues on the plant floor.
SAOG Cyber supports organizations with OT asset and architecture reviews, network segmentation strategy, risk assessments, governance and management-of-change design, and OT incident-readiness planning.