Questions organizations ask when a contract requires NIST SP 800-171: Rev. 2 versus Rev. 3, who must comply, the system security plan, SPRS scores, assessments, cost and scoping CUI into an enclave.
What changed between SP 800-171 Rev. 2 (110 requirements) and Rev. 3 (97 requirements), which revision DoD contracts and CMMC require as of October 2026, the proposed FAR rule that would move contractors to Rev. 3, and how to use NIST's change analysis to plan the transition.
Which organizations and systems SP 800-171 applies to: the federal CUI rule behind it, the DFARS clause that puts it in DoD contracts and subcontracts, the scope limited to systems that handle or protect CUI, and the pending governmentwide FAR rule for civilian agency contractors.
What a NIST SP 800-171 system security plan (SSP) must contain under Rev. 3 requirement 03.15.02 and Rev. 2 requirement 3.12.4, why DoD and CMMC assessments cannot proceed without one, what else the SSP must document for scoping and service providers, and what keeping it current costs.
How the NIST SP 800-171 score posted in the Supplier Performance Risk System (SPRS) is calculated: the 110-point DoD Assessment Methodology, weighted deductions, partial credit, how plans of action are treated, posting and currency rules in the DFARS, the CMMC scoring rule and the September 2026 DFARS deviation.
How organizations are assessed against NIST SP 800-171: SP 800-171A procedures and methods, self-assessments versus Government and CMMC third-party assessments, what evidence assessors expect, POA&M and closeout rules, artifact retention, and how the July 2026 CMMC suspension changed who assesses.
What implementing NIST SP 800-171 costs according to US Government regulatory impact analyses: labor and hardware or software estimates by business size, recurring costs, SSP upkeep, enhanced SP 800-172 costs, CMMC assessment costs, and what drives the spread.
Limiting NIST SP 800-171 scope by isolating CUI in an enclave or separate security domain: what NIST permits, how CMMC scoping rules treat separated, security and out-of-scope assets, VDI and cloud options, and the requirements that make the isolation hold.
A checklist of what a defense contractor must have in place to show NIST SP 800-171 compliance: scope, system security plan, plan of action, SPRS score, incident reporting readiness, cloud provider checks and subcontract flow-down, with the rule behind each item.
What NIST SP 800-172 adds on top of SP 800-171 for CUI tied to critical programs and high value assets: who can require it, the 2021 version and the Rev. 3 draft, the 24 requirements CMMC Level 3 selects, and the Government's cost estimates for implementing it.
What organization-defined parameters are in SP 800-171 Rev. 3, how many requirements have them, who sets the values when an agency does not, the DoW CIO ODP values the proposed FAR rule points to, and how ODPs change scoping and evidence.
The requirements that exist in SP 800-171 Rev. 3 but not in Rev. 2 or CMMC Level 2: the three added families, policy and procedures, information location, component inventory, unsupported components, external system services and supply chain risk management, and why they appeared.
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