Defensive Layer Classification

Control Statement

Every element on the terrain shall be classified to exactly one defensive layer: identity, devices, networks, applications and workloads, data, operational technology, workforce, facilities, or supply chain. Elements that enable maneuver across layers rather than constituting ground — visibility and analytics, automation and orchestration, governance — shall be classified to the cross-cutting domain.

Purpose. To make posture summable and comparable by layer, and to force an explicit ownership decision for every element.

Discussion

Classification is what allows posture to be rolled up and compared. The one-layer rule is what keeps the matrix partitionable: coverage summed across layers must equal total coverage, and an element counted twice inflates both. The failure this correction addresses is structural — a framework that added four terrain layers in v2.0 and v3.0 while leaving the classification control at five made those layers doctrinally present and practically unscoreable.

Goals and Metrics

A metric that cannot come out badly is not a metric. Each of these is capable of reporting that the control is not working.

Accountability

Exactly one role is accountable, and every other role carries at least Informed — no control in the published catalog leaves a role with zero relationship to it. That is a stated property of how these were authored, not a coincidence, and not a claim that every role's work is worth equal attention here.

Inputs and Outputs

Activities

1. L2Classify every element to exactly one of the nine terrain layers, or to the cross-cutting domain where the element enables movement rather than being ground.
2. L2Flag unclassified elements automatically rather than relying on review.
3. L2Record the classification against the element in the register.
4. L3Where an element plausibly spans layers, assign it to the layer whose loss would defeat it, and cross-reference from the others rather than duplicating.
5. L3Treat unclassified elements as findings with an owner and a due date.
6. L3Reconcile layer totals to the full inventory each cycle; a shortfall means elements are unclassified, an excess means one is double-counted.
7. L3Record rationale for any classification a reviewer would find surprising, so the decision survives its author.
8. L4Trend reclassification rate; a layer with high churn indicates the criteria are ambiguous rather than that the estate is changing.
9. L4Measure the population of each of T6–T9 and escalate where a declared terrain layer holds no classified elements at all.
10. L5Refine the layer criteria where reclassification patterns show a boundary that practitioners cannot apply consistently.

Measurement

Evidence and Assessment

Related Guidance

Position in the Chain

Derived from the other controls’ own declarations, so the two directions cannot disagree.

Where This Control Is Used

Derived, in every case, from the declaration at the other end: the forms whose techniques name this control, the artifacts whose producing and consuming controls include it, the layers whose control lists name it, and the roles its own accountability chart puts to work. Nothing here is authored on this page, so the sheet cannot claim an edge the other end does not.