Marking and labeling
Showing an asset's classification: human-readable markings on documents, screens and media, and machine-readable labels that a system uses to enforce access decisions.
Marking and labelling make an asset’s data classification visible, so the right handling requirements go with it. Everyday usage treats the two words loosely, but NIST SP 800-53 Rev. 5 separates them. Marking is the human-readable form: a banner on a document, a header on a screen, a sticker on a removable drive or backup tape (control MP-3, Media Marking). Labelling is the association of security attributes with subjects and objects inside a system, where software can read and act on them (control AC-16, Security and Privacy Attributes).
The two serve different readers. A marking tells a person how to treat what is in front of them; a security label lets a system, such as one enforcing mandatory access control, compare an object’s level with a subject’s clearance. Both carry the decision of the data owner, and both have to be updated when data is reclassified or declassified. Portion marking extends the idea to the individual sections of one document.
Exam relevance: a scenario may describe sensitive media found without a marking, or ask what lets a system enforce classification automatically. Candidates are expected to link human-readable markings to how people handle material and system labels to automated enforcement, and to see both as consequences of classification rather than substitutes for it.