NIST SP 800-171 Rev 2 · 3.5 Identification & Authentication
3.5.5 Prevent identifier reuse
Prevent reuse of identifiers for a defined period.
- SPRS weight
- 1
- 1 point deducted from 110 when not implemented.
- CMMC level
- L2
- Level 2 only; not among the 17 Level 1 practices.
- Assessment objectives
- 2
- From NIST SP 800-171A, each one a “determine if” an assessor answers.
What an assessor checks
NIST SP 800-171A breaks 3.5.5 into 2 objectives. Every one has to be met for the requirement to be met; a partial answer scores as not implemented.
- [a]Determine if a period within which identifiers cannot be reused is defined.
- [b]Determine if reuse of identifiers is prevented within the defined period.
- Examine
- [SELECT FROM: Identification and authentication policy; procedures addressing identifier management; procedures addressing account management; security plan; system design documentation; system configuration settings and associated documentation; list of system accounts; list of identifiers generated from physical access control devices; other relevant documents or records].
- Interview
- [SELECT FROM: Personnel with identifier management responsibilities; personnel with information security responsibilities; system or network administrators; system developers].
- Test
- [SELECT FROM: Mechanisms supporting or implementing identifier management].
If it is open: POA&M eligibility
May be carried on a Level 2 POA&M · 1 point deducted
A 1-point requirement outside the six named exclusions - eligible to carry, and NOT MET until a closeout assessment confirms it.
A POA&M is only permitted at a score of 88 or above, and closes in one 180-day window. Check a full gap list or compute your score.
Where 3.5.5 maps
NIST SP 800-53 Rev 5
- AC-2 Account Management
- IA-4 Identifier Management
NIST CSF 2.0
- Identities are managed Identity Management, Authentication and Access Control
SOC 2
No direct mapping.
Query it from your own tools
This page and the MacTech CMMC MCP server render the same dataset. Ask your assistant and it will answer from the methodology, not from memory.
lookup_control 3.5.5 get_assessment_objectives 3.5.5 generate_poam_entries ["3.5.5"]
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