This post explains how to design and implement an audit-ready log review policy to satisfy CMMC AU.L2-3.3.3 in the Compliance Framework, with practical templates, checklists, technical implementation notes, and small-business examples you can adopt immediately.
What AU.L2-3.3.3 Requires (high level)
AU.L2-3.3.3 in the Compliance Framework is an Audit & Accountability requirement focused on regular, documented review of system and security logs at Level 2 rigor. The goal is to ensure logged events that indicate security-relevant activity—authentication anomalies, privilege changes, device or network anomalies, data access patterns—are reviewed on a consistent schedule, triaged, and retained as evidence for audits. For a small organization this means defining frequency, scope, responsibilities, acceptance criteria, and evidence retention so an auditor can verify the control works and is repeatable.
Essential Components of an Audit-Ready Log Review Policy
A compliant policy should include: scope (systems, applications, network devices, cloud services), log sources and fields to retain (timestamps, user ids, source/destination IPs, event IDs), review cadence (daily automated triage + weekly manual review + monthly audit), roles and responsibilities (log owner, analyst, escalation manager), evidence retention standards (how long and where logs and review artifacts are kept), time synchronization (NTP), log integrity controls (WORM, hashing or signed archives), and escalation rules (SLA for investigation and remediation). Include specific acceptance criteria such as "failed-login spikes > 50% over baseline within 15 minutes = triage" so auditors can test the decision logic.
Practical Implementation Steps for Compliance Framework
1) Inventory your log sources: list servers, endpoints, firewalls, IDS/IPS, application logs, cloud audit logs (AWS CloudTrail, Azure Activity Logs, GCP Audit Logs), identity providers (Okta, Azure AD), and EDR tools. 2) Centralize collection: deploy a lightweight forwarder (syslog-ng, fluentd, Winlogbeat) into a secured ingestion point or managed SIEM (Elastic SIEM, Splunk Cloud, Sumo Logic, or your MSSP). 3) Normalize events into a canonical schema (timestamp, host, user, event_type, severity, message) and store in JSON/parquet for search. 4) Implement time sync and integrity: ensure NTP and apply HMAC or store immutable archives (S3 with object lock/WORM). 5) Create automated detection rules for high-volume, high-fidelity conditions (e.g., multiple failed logins, disabled MFA attempt, privilege change events) and schedule automated daily reports plus a manual weekly review by a named reviewer. 6) Document workflows that convert alerts into tickets with evidence attachments and closure notes.
Technical Details and Example SIEM Rules
Use concrete detection rules and queries so reviews are objective. Examples for a small business SIEM: a) Failed authentication threshold: count(auth.failure) by user within 15m > 10 => generate high-priority alert. b) Privilege escalation: event_id in [4648,4670] and target_group == "Domain Admins" => alert. c) Lateral movement heuristic: successful RDP from internal host A to host B followed by SMB session to another host C within 10 minutes => medium alert. Store queries and thresholds in the policy so auditors can run them. Also specify retention times (e.g., authentication and privilege logs retained for 1 year online, 3 years archived offline) and export formats (CSV/NDJSON) so evidence can be produced rapidly.
Small Business Scenario: Implement with Limited Staff
A two-office small business can meet AU.L2-3.3.3 without a full SOC: forward all logs to a low-cost cloud SIEM or MSSP; configure three automated rules (failed logins, privilege changes, external data exfil) and daily summary emails to the administrator; assign weekly manual review to the IT lead with a checklist. Use inexpensive immutable cloud storage (S3 with Object Lock) for monthly snapshots and store review artifacts (tickets, annotated alerts, signed review logs) in a single audit folder with a naming convention like "audit/log-review/YYYY-MM-DD_[reviewer].zip". This approach creates an auditable trail while minimizing headcount and complexity.
Templates and Checklists
Below are ready-to-use templates you can paste into your policy document and a practical checklist for each review cycle.
Log Review Policy (Template)
Title: Log Review Policy - AU.L2-3.3.3 (Compliance Framework)
Scope: [List systems, cloud services, network devices, applications]
Objectives:
- Ensure security-relevant events are reviewed and triaged
- Provide evidence for compliance audits
Roles:
- Log Owner: [name/email]
- Reviewer: [name/email]
- Escalation Manager: [name/email]
Review Cadence:
- Automated triage: real-time
- Daily summary: automated email to Reviewer
- Weekly manual review: documented review note
- Monthly audit: sampling of alerts and closure evidence
Log Retention:
- Authentication and access logs: 12 months online, 36 months archived
- Syslogs and app logs: 6 months online, 24 months archived
Integrity & Time Sync:
- NTP servers: [list]
- Archive hashing: SHA-256, stored with logs
Escalation SLA:
- High: 4 hours, Medium: 24 hours, Low: 7 days
Evidence & Naming:
- Store tickets, annotated alerts, review spreadsheets in /audit/log-review/YYYY-MM
- File format: NDJSON for logs, PDF for signed review notes
Approval:
- Policy owner signature: __________________ Date: ________
Weekly Log Review Checklist
- [ ] Confirm all log collectors are reporting (check for gaps > 5 minutes)
- [ ] Verify NTP sync on all collectors and key servers
- [ ] Open SIEM weekly summary and review top 10 alerts by severity
- [ ] Triage each alert: assign ticket, add evidence (screenshots, query), set SLA
- [ ] Review privilege-change events in the last 7 days and validate business need
- [ ] Review failed-auth spikes and confirm if caused by user error or attack
- [ ] Archive reviewed alerts and save review notes to /audit/log-review/YYYY-MM
- [ ] Sign and timestamp the review log (digital signature acceptable)
Risks of Not Implementing AU.L2-3.3.3 Properly
Failing to implement this control creates multiple risks: undetected breaches and extended dwell time, inability to meet legal or contractual evidence requests, failed audits with potential fines or remediation orders, and loss of customer trust if a breach is discovered but cannot be investigated properly. Operationally, a lack of standardized review practices leads to inconsistent triage, missed false positives that hide real incidents, and no repeatable evidence trail for auditors.
Compliance Tips and Best Practices
Keep the policy simple and enforceable: start with a small set of high-fidelity rules and extend over time. Use naming conventions and consistent artifact storage to speed evidence collection during audits. Automate as much as possible (daily reports, collector health checks, ticket creation) to make manual reviews focused on triage and context. Maintain a change log for the policy and detection rules (who changed what and why) to show maturity to auditors. Finally, run quarterly tabletop exercises using historic alerts so reviewers can demonstrate response and documentation to auditors.
Summary: AU.L2-3.3.3 is achievable for organizations of any size by codifying scope, cadence, roles, thresholds, integrity controls, and evidence handling into a clear log review policy, then operationalizing it with centralized collection, automated triage, a small set of SIEM rules, and a repeatable checklist. Use the provided template and checklist to build your policy, capture artifacts consistently, and reduce audit friction while improving your security posture.
