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Controls / Access Control / 3.1.8
3.1.8
AC.L2-3.1.8 · Level 2

Limit unsuccessful logon attempts.

NIST SP 800-171 Rev 2 · §3.1.8

Limit unsuccessful logon attempts.

Assessment objectives

From NIST SP 800-171A · 2 objectives must be met to satisfy this control
3.1.8[a] the means of limiting unsuccessful logon attempts is defined.
Examine
[SELECT FROM: Access control policy; procedures addressing unsuccessful logon attempts; security plan; system design documentation; system configuration settings and associated documentation; system audit logs and records; other relevant documents or records].
Interview
[SELECT FROM: Personnel with information security responsibilities; system developers; system or network administrators].
Test
[SELECT FROM: Mechanisms implementing access control policy for unsuccessful logon attempts].
3.1.8[b] the defined means of limiting unsuccessful logon attempts is implemented.
Examine
[SELECT FROM: Access control policy; procedures addressing unsuccessful logon attempts; security plan; system design documentation; system configuration settings and associated documentation; system audit logs and records; other relevant documents or records].
Interview
[SELECT FROM: Personnel with information security responsibilities; system developers; system or network administrators].
Test
[SELECT FROM: Mechanisms implementing access control policy for unsuccessful logon attempts].

What we look for in practice

The following are placeholder notes that should be refined based on practice experience.

What assessors look for in practice. Documented evidence that this control is implemented across all CUI-handling systems within scope. Specific artifacts vary, but expect requests for written procedures, system configurations, and operational records demonstrating the control is active.

Common failure patterns. Typical issues include incomplete documentation, inconsistent implementation across systems, and missing periodic review records. Refine this section as your practice accumulates direct assessment experience.

Strong evidence looks like. Formal policy referencing this control, technical configurations demonstrating enforcement, periodic review logs with sign-off, and procedures for handling exceptions.

Scoring and POA&M context. 1-point control under the DoD Assessment Methodology. Lower scoring impact, but still required for full compliance. POA&M-eligible — deferral up to 180 days is allowed under conditional certification per 32 CFR 170.21.