- Enumerate what is listening: a port scan of your own estate against an approved-services list finds what documentation forgot.
- Disable the known-bad legacy set deliberately — SMBv1, Telnet, unencrypted management interfaces — and record the decision per protocol.
- Re-check on a cadence, because updates and new software re-enable services with no announcement.
3.4.7OFFICIAL STATEMENT BELOWDERIVED REQUIREMENTPENDING NIST SME REVIEW
3.4.7 — Nonessential functionality restriction
3.4 Configuration Management · NIST SP 800-171 Rev. 2 · The heading label is this site's navigational shorthand; the official language is the statement below.
Official requirement statement (verbatim)
Restrict, disable, or prevent the use of nonessential programs, functions, ports, protocols, and services.
NIST SP 800-171 Rev. 2 — Protecting CUI in Nonfederal Systems ↗NIST SP 800-171A — Assessing Security Requirements for CUI ↗Independent interpretation
What this requirement is after
The follow-through on least functionality: nonessential programs, ports, protocols, and services are actually restricted, disabled, or prevented — not just frowned upon. Legacy protocols nobody remembers enabling are the classic finding here.
Across revisions
Withdrawn as a standalone requirement in Rev. 3 (the 03.04.07 slot is marked withdrawn); restricting nonessential functions is carried inside Least Functionality, 03.04.06.
Mapped practices
Brilliant at the Basics practices that support this requirement
No practice maps to this requirement — deliberately.
The campaign’s twenty practices are a priority list, not a control catalog, and none of them works this requirement’s substance directly. It still applies to you if it is in your contract’s scope: address it through your own implementation and the related artifacts below, and treat the absence of a mapping here as honesty, not permission to skip it.
Doing the work
Implementation considerations and evidence
- The approved ports, protocols, and services list
- Scan results reconciled against that list, dated and repeated
Artifacts
Templates and worksheets with a mapped relationship
No artifact in the library names this requirement yet. The library index groups everything by category and practice.
The other revision
Where this lands in Rev. 3
Provenance
Sources and review status
| Primary sources | NIST SP 800-171 Rev. 2 — Protecting CUI in Nonfederal Systems · NIST SP 800-171A — Assessing Security Requirements for CUI |
|---|---|
| Review status | Pending NIST SME review |
| Content version | 1.0 |
| Updated |