Definition
Employ a mechanical locking device for securing moveable portions of physical barriers (e.g., doors, gates, drawers) in a secured position.
How it works
A physical mechanism which has a associated credential which when entered enables the lock bolt to operate, i.e. open or close.
Considerations
- Consider that locks for specified materials should adhere to relevant regulations.
- Lock equipment cabinets when not needed for operation or safety; set OT asset keys of devices (e.g., PLCs and safety systems) to the “RUN” position unless otherwise specified.
- Locks and all associated hardware should be properly installed, operable, and free of substantive indications of tampering.
- Records should be maintained concerning maintenance performed, access, and any possible tampering marks or associated incidents.
- For locks operated by a physical key, a key management system should be implemented to manage and secure physical keys.
- Key locks should provide a high degree of resistance to opening by force and tampering techniques.
Implementation perspective
Physical Locking should be treated as a technical defensive capability rather than a product checkbox. In practice, teams should define the protected scope, the conditions under which the technique acts, and the observable evidence that demonstrates the intended behavior. For this technique, likely engineering context includes the relevant system, activity, and evidence sources.
Use the technique to create a logical or physical boundary that limits access, execution, communication, or movement.
Questions to ask
- What is being isolated, from whom or what, and under which conditions?
- Which flows or operations remain explicitly allowed across the boundary?
- What happens when the isolation mechanism fails or loses policy context?
- How is the boundary tested for alternate paths, bypasses, and unintended dependencies?
Evidence and validation
- Architecture and data-flow diagrams showing the isolation boundary
- Policy, rule, or configuration exports from enforcing components
- Tests of allowed, denied, and failure-state behavior
- Monitoring evidence for boundary violations and policy changes
Common failure patterns
- The intended boundary has undocumented alternate paths or inherited trust relationships.
- Rules accumulate without ownership, review, or removal of obsolete exceptions.
- Isolation is assumed from network location while application, identity, or management paths remain open.
This implementation perspective is original Bare Metal Cyber educational content. It does not replace the official D3FEND definition or establish that a specific product implements the technique.
Technique hierarchy
Top-level family
Parent techniques
Direct child techniques
None listed at this level.
Artifacts and ontology entities
These relationships describe how D3FEND connects a defensive technique to artifacts or other ontology entities. They describe graph semantics, not a product certification.
Explicit technique relationships
Authoritative sources
- Open this technique on the official D3FEND website ↗
- Open the official ontology resources ↗
- REGULATORY GUIDE 5.12 GENERAL USE OF LOCKS IN THE PROTECTION AND CONTROL OF: FACILITIES, RADIOACTIVE MATERIALS, CLASSIFIED INFORMATION, CLASSIFIED MATTER, AND SAFEGUARDS INFORMATION ↗U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REGULATORY RESEARCH · U.S. NUCLEAR REGULATORY COMMISSION OFFICE OF NUCLEAR REGULATORY RESEARCH · GuidelineReference
- Guide to Operational Technology (OT) Security ↗NIST · InternetArticleReference
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