Your biggest OT risk may not be a new exploit.
It may be a 20-year-old script nobody owns, running a process nobody fully understands.
In many OT environments, code outlives the people, vendors, documentation, and assumptions that created it. PLC logic, HMI scripts, batch files, historian queries, custom middleware, and one-off integrations quietly become part of the control system’s nervous system.
Until an outage, audit, migration, or incident response effort forces the question:
What does this actually do?
For OT CISOs, undocumented logic is not just a maintenance problem. It is an active operational and security risk.
Why it matters:
1. Hidden dependencies can break recovery plans
A “minor” server change can disrupt a process because an undocumented script still points to an old hostname, share, or database.
2. Tribal knowledge creates single points of failure
If only one retired engineer understood the logic, the organization does not own the risk. It has inherited uncertainty.
3. Security reviews miss what is not inventoried
You cannot assess, monitor, patch, or segment logic you do not know exists.
4. Incident response slows down under pressure
During an OT event, teams need confidence. Unknown code creates hesitation, false assumptions, and unsafe decisions.
CISOs should treat legacy knowledge discovery as a formal program, not an informal cleanup task.
Start with:
• Inventory custom scripts, macros, logic blocks, and integrations
• Map dependencies between assets, processes, vendors, and data flows
• Interview operators, engineers, and maintainers before knowledge leaves
• Document intent, failure modes, and safe rollback procedures
• Prioritize code tied to safety, uptime, remote access, and critical production
• Review legacy logic during MOC, audits, and incident exercises
The goal is not to modernize everything at once.
The goal is to know what you are relying on before it fails, gets exploited, or blocks recovery.
In OT, retired knowledge is never truly retired if the process still depends on it.
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