49 CFR § 1520.13 - Marking SSI.
(a) Marking of paper records. In the case of paper records containing SSI, a covered person must mark the record by placing the protective marking conspicuously on the top, and the distribution limitation statement on the bottom, of -
(1) The outside of any front and back cover, including a binder cover or folder, if the document has a front and back cover;
(2) Any title page; and
(3) Each page of the document.
(b) Protective marking. The protective marking is: SENSITIVE SECURITY INFORMATION.
(c) Distribution limitation statement. The distribution limitation statement is:
(d) Other types of records. In the case of non-paper records that contain SSI, including motion picture films, videotape recordings, audio recording, and electronic and magnetic records, a covered person must clearly and conspicuously mark the records with the protective marking and the distribution limitation statement such that the viewer or listener is reasonably likely to see or hear them when obtaining access to the contents of the record.