What evidence do auditors commonly ask for on AU-4 Audit Log Storage Capacity?

Audit and accountability policy; Procedures addressing audit storage capacity; System security plan; Privacy plan; System design documentation; System configuration settings and associated documentation.

What is the most common gap auditors find on AU-4?

Audit log storage capacity was allocated without reference to the organization-defined log retention requirements

NIST SP 800-53 Rev 5 · AU - Audit and Accountability

`AU-4` Audit Log Storage Capacity

Allocate audit log storage capacity to accommodate organization-defined audit log retention requirements.

Source: NIST SP 800-53 Rev 5, AU-4. The statement above is our statement of the clause, read from the published text and cited so you can check it against the official text, not the instrument verbatim. Open NIST SP 800-53 Rev 5 in the compliance library.

Base controls and their enhancements. Which apply follows the baseline you are assessed against (for example FedRAMP Moderate or High, or the low, moderate and high baselines of SP 800-53B). Text in square brackets is a parameter your organisation sets.

artefacts

held by a system

at each review

hard

to go live

Policy repository / GRC workspace

where the evidence lives

teal = a system already holds it · olive = produced at each review. To go live: easy when half or more of the artefacts are already held by a system, moderate from a quarter to a half, hard below a quarter.

These are the artefacts auditors commonly ask for on this requirement, our guidance rather than text from the standard. Your assessor decides what is sufficient in your context, and asks for samples across the period when a report covers one.

system holds itEvidence a system already holds

none for this control

periodic reviewEvidence produced at each review

Audit record storage capability for system components · Policy repository / GRC workspace
System audit records · Policy repository / GRC workspace
Test of Audit record storage capacity and related configuration settings · Cloud console / configuration management

governing documentDocuments that govern the control

Audit and accountability policy · Policy repository / GRC workspace
Procedures addressing audit storage capacity · Policy repository / GRC workspace
System security plan · Policy repository / GRC workspace
Privacy plan · Policy repository / GRC workspace
System design documentation · Policy repository / GRC workspace
System configuration settings and associated documentation · Policy repository / GRC workspace
Audit record storage requirements · Policy repository / GRC workspace

First move

No system holds this evidence for you: it is people and documents. Reminders and routing to the owner still save time. Put the document under version control with an owner and review date, and log each review as a record with reviewer and date.

Common gaps auditors find

Audit log storage capacity was allocated without reference to the organization-defined log retention requirements
Allocated log storage cannot hold records for the defined retention period, so older records are overwritten early

Do this for your whole sheet

Paste the rows you run your controls from and get this mapping for every control at once, with the periodic-review ones flagged and a first move per row. No account for the first run.

Build my evidence sheet

AU-3(3) Content of Audit Records | Limit Personally Identifiable Information Elements · AU-4(1) Audit Log Storage Capacity | Transfer to Alternate Storage