NIST Special Publication 800-171 defines security requirements for protecting Controlled Unclassified Information (CUI) when it resides in nonfederal systems and organizations. If CMMC Level 2 is in your future, 800-171 is the control language you will live in.
Why 800-171 exists
Federal agencies need contractors to safeguard sensitive but unclassified information without forcing every supplier onto federal networks. 800-171 provides a consistent requirements set for confidentiality of CUI in contractor environments.
How it relates to CMMC
CMMC Level 2 is built around implementing these practices (with DoD assessment methodology layered on top). Understanding 800-171 early prevents “tool shopping” without control coverage.
What “implementation” means
For each requirement, you need an implemented control and a way to show it: configuration, process, and evidence. That is why the SSP and POA&M matter as much as the firewall.
SMB-focused priority themes
- Identity and access (MFA, least privilege, admin control)
- Device security and patching
- Email and collaboration hardening
- Audit logging sufficient to investigate incidents
- Incident response that people can actually run
- Backup/recovery tested under time pressure
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