The means used to associate a set of security attributes with a specific information object as part of the data structure for that object.
See the following under Security Label for more information:
Explicit or implicit marking of a data structure or output media associated with an information system representing the FIPS 199 security category, or distribution limitations or handling caveats of the information contained therein.
See NIST SP 800-18 Rev. 1 under Security Label for more information.