Meeting AU.L2-3.3.3 — the requirement to review and update logged events — is about more than keeping heaps of logs: it’s about creating a repeatable SOP that defines which events matter, who reviews them, how often, and how changes are controlled and evidenced for audit against NIST SP 800-171 Rev.2 / CMMC 2.0 Level 2.
Why an SOP is required and how it maps to the Compliance Framework
An SOP documents the process that satisfies AU.L2-3.3.3: it demonstrates the organization consistently reviews logged events and updates logging rules as systems and risks change. For Compliance Framework practitioners, the SOP ties technical controls (SIEM, system logging, time sync, retention) to governance artifacts (roles, schedules, evidence retention) so auditors can see implemented policy → procedure → evidence flow.
Core elements of a practical SOP (implementation notes)
Start your SOP with scope, roles, and required technical assets: list systems in scope (domain controllers, file servers, mail, endpoints, cloud workloads), logging collection points (syslog servers, Windows Event Forwarding, cloud audit logs), and the SIEM or log aggregator in use (Elastic Stack, Wazuh, Splunk, Sumo Logic, etc.). Specify time sources (NTP servers) and cryptographic integrity (log signing or WORM/immutability) so timestamps and tamper-evidence are auditable. For a small business, limit initial scope to high-risk assets (AD, email, file shares, VPN) and expand iteratively.
Step-by-step actionable procedure
1) Inventory and baseline: create an asset-log matrix (asset, OS, log types produced, forwarding method, owner). 2) Define the initial event catalog aligned with AU.L2-3.3.3: critical events (authentication success/failure — Windows 4624/4625, Linux auth failures; privilege changes — Windows 4672; process creation — Windows 4688; file access for sensitive directories — Linux auditd or Windows 4663; cloud console/API activities). 3) Configure collection: enable auditd rules on Linux, enable Advanced Audit Policy on Windows with WEF and a universal forwarder; use TLS for syslog over TCP (syslog-ng with TLS on port 6514 instead of UDP 514). 4) Implement retention and integrity: hot retention for 90 days in SIEM for investigations, archive to immutable object storage (S3 with Object Lock or on-prem WORM) for 1+ years depending on contractual DOD requirements. 5) Schedule and automate reviews: daily automated alerts, weekly summary review, monthly rule tuning, quarterly full event-catalog review, and annual SOP review.
How to review and when to update logged events
Define measurable review activities: triage alerts daily and record outcomes in a ticketing system; run weekly reports of top 50 event types, event volume anomalies, and “quiet” systems that stopped sending logs. Use the monthly tuning meeting to add/remove events: e.g., reduce noise by disabling verbose application debug logs in production and enable more granular file access monitoring for new sensitive directories. All updates must go through a simple change control entry in the SOP: proposed change, rationale (new system, false positive reduction, new data type), test evidence, approval (system owner + security), effective date, and rollback plan.
Templates and evidence you should collect (included)
Use concise templates so small teams can adopt them. Include: a Review Checklist, an Event Update Request form, and a Log Review Report template that captures dates, reviewers, findings, tickets opened, and artifacts (screenshots, SIEM queries, exported CSV). Keep stored SOP versions and evidence in a compliance repository (encrypted file share or GRC tool) with access control and retention rules to demonstrate auditability.
Template: Log Review Checklist (example)
- Review period: [start - end] - Systems checked: [list] - SIEM health: collectors online? [yes/no] - NTP status: synchronized? [yes/no] - Top 10 event types for period: [list] - Missing expected logs? [yes/no + details] - New noisy events identified? [yes/no + IDs] - Incidents escalated? [ticket IDs] - Reviewer name & signature:
Template: Event Update Request (example)
- Request ID: - Date: - Requester: - System(s) affected: - Current event rule: - Proposed change (add/remove/update): - Reason/risk addressed: - Test evidence (query output, sample events): - Approvals: System Owner / Security Officer / Compliance - Effective date:
Real-world small business scenario and risk explanation
Scenario: a 50-employee engineering firm relied only on local workstation logs and occasional manual checks. A contractor exfiltrated sensitive design files via a cloud sync client — no alerts fired because file access to the local directory wasn’t being logged centrally. Without an SOP to review and update logged events, that gap remained invisible. The consequences: lost IP, contractual breach with a prime contractor, and failed CMMC assessment. By contrast, a simple SOP that added file-access monitoring for project directories, forwarded events to a SIEM, and required weekly review would have generated an alert on mass file reads and outbound connections, allowing containment within hours.
Compliance tips, best practices, and concluding summary
Best practices: enforce least privilege to reduce noise, use contextual fields (username, source IP, process name) in logs for faster triage, baseline normal event volumes and use anomaly detection, and keep SOPs lean and versioned. Automate as much as possible (health checks, dashboards, scheduled reports) but keep a human-in-the-loop for rule updates. Make evidence collection part of the daily workflow so auditors see tickets and reports, not just configuration files. The risk of not implementing this SOP includes missed intrusions, undetected insider threats, non-compliance findings, and potential contract or revenue loss.
Summary: Build an AU.L2-3.3.3 SOP by scoping assets, defining and cataloging important events, configuring secure collection and retention, scheduling automated and manual reviews, and managing updates via a formal change process — using the provided templates will accelerate adoption and create audit-ready evidence for NIST SP 800-171 Rev.2 / CMMC 2.0 Level 2 compliance.
