The answer is no: in cmmc manual log review vs mdr, an MDR provider may monitor, investigate, and escalate security alerts, but it does not automatically satisfy AU.L2-3.3.3’s requirement to review and update the events your systems log. For CMMC 2.0 Level 2, your company needs an accountable process for deciding when logged event types are reviewed, documenting that review, and changing audit configurations when the review identifies a gap. MDR is an operational security service; AU.L2-3.3.3 is primarily an audit-configuration governance requirement.
What is the difference between manual log review and MDR?
“Manual log review” usually means a person examines audit records produced by systems—such as sign-in failures, administrator actions, or firewall alerts—to identify suspicious activity. That activity is relevant to NIST SP 800-171 Rev. 2 controls AU.L2-3.3.5 and AU.L2-3.3.6, which address reviewing and reporting audit records.
Managed Detection and Response, or MDR, is an outsourced security operation. An MDR provider typically collects telemetry from endpoint, identity, email, and network tools; applies detections; has analysts investigate alerts; and notifies your internal contact when action is needed. Depending on the agreement, the provider may also isolate an endpoint or help contain an incident.
AU.L2-3.3.3 is different from both concepts. Its requirement is to review and update logged events. The implementation notes make the distinction explicit: this practice focuses on configuring the auditing system, not on reviewing the audit records generated by selected events. In practical terms, the question is not merely, “Did someone look at alerts?” It is, “Did we periodically decide whether our selected event types remain appropriate, and did we update those selections when needed?”
What does a manual review look like in a real environment?
Consider a company using Microsoft 365 Business Premium, Microsoft Defender for Business, and a SonicWall firewall. A quarterly review may show that Windows endpoint telemetry captures malware detections and antivirus exclusions but does not consistently capture local administrator-group changes. The security lead enables the relevant Windows Advanced Audit Policy setting, forwards Event ID 4732 to Microsoft Sentinel or the MDR’s SIEM, and records the reason for the change.
That configuration decision and evidence trail support AU.L2-3.3.3. If an analyst later investigates Event ID 4732 because it appears suspicious, that is audit-record review and incident response work—not the core activity covered by this specific practice.
What does MDR look like in the same environment?
The MDR provider may receive Defender for Endpoint telemetry, watch for suspicious PowerShell execution, impossible-travel sign-ins, ransomware behavior, and privilege escalation, then call the company’s designated contact if it finds a credible threat. The provider may recommend enabling additional logging or may identify a blind spot during onboarding. Those are valuable inputs, but the provider’s alert-monitoring service alone does not prove that the organization follows a defined process for reviewing and updating its selected logged event types.
How does cmmc manual log review vs mdr compare for AU.L2-3.3.3?
| Comparison point | Manual audit-record review | MDR service | AU.L2-3.3.3 expectation |
|---|---|---|---|
| Primary purpose | Find suspicious, anomalous, or policy-violating activity in records already collected. | Detect, investigate, and escalate threats through managed analysts and detection tooling. | Confirm that the organization is logging the right event types and revises selections when needed. |
| Typical cadence | Daily, weekly, or triggered by alerts and incidents. | Continuous monitoring, often 24x7. | Defined periodic review, such as quarterly and after major system, threat, or incident changes. |
| Concrete evidence | Analyst ticket, review checklist, SIEM query result, or investigation notes. | MDR monthly report, incident ticket, escalation email, and service-level reports. | Audit configuration review record, approved changes, current log-source inventory, and configuration screenshots or exports. |
| Example tool activity | Reviewing Microsoft Sentinel incidents for repeated failed VPN sign-ins. | Huntress MDR investigating Defender alerts and recommending endpoint isolation. | Enabling Windows “Audit Security Group Management,” retaining Event IDs 4728, 4732, and 4756, and documenting why. |
| Who is accountable | An internal administrator, security employee, or contracted reviewer. | The provider performs agreed monitoring tasks; the customer retains governance responsibilities. | A named company owner must approve the process and ensure review-driven updates occur. |
| Does it independently satisfy AU.L2-3.3.3? | No. Looking at records does not necessarily prove the logged-event configuration was reviewed. | No. Continuous monitoring does not automatically establish configuration governance. | Yes, when the defined review process is followed and resulting updates are evidenced. |
Where do companies confuse MDR with this CMMC control?
The most common mistake is presenting an MDR contract, dashboard, or monthly threat report as complete evidence for AU.L2-3.3.3. Those documents can show that a provider is watching security data. They do not necessarily show which event categories are enabled, when the organization evaluates them, or whether gaps identified through a review are corrected.
A second mistake is treating “manual log review” as the control’s exact requirement. For this practice, assessors are not principally asking whether an employee reads thousands of raw Windows, firewall, or cloud logs. They are looking for a defined process that determines when logged events are reviewed and whether the event types being logged are still appropriate. The three key objectives are straightforward:
- A process defines when the organization reviews logged events.
- The event types being logged are reviewed according to that process.
- The organization updates event types based on the review.
For a COO managing compliance spend, this distinction matters because it prevents buying the wrong evidence. An MDR subscription may be a sound investment for risk reduction and may reduce the internal labor needed for continuous monitoring. But it should not be budgeted as a substitute for an owner, a periodic audit-configuration review, and controlled changes to logging settings.
What would an assessor reasonably expect to see?
An assessor evaluating AU.L2-3.3.3 will generally expect evidence that ties policy, operating practice, and technical settings together. A concise review record can be more useful than a large volume of unrelated alert reports. For example:
Audit Event Configuration Review Review cadence: Quarterly and after a security incident, major system change, or new CUI system. Date: 2026-06-30 Reviewers: IT Manager and MDR Service Delivery Manager Systems reviewed: Microsoft 365, Defender for Endpoint, Windows Server, SonicWall VPN Finding: Privileged group membership changes were not forwarded from two file servers. Decision: Enable Audit Security Group Management; forward Event IDs 4728, 4732, 4756. Change ticket: CHG-2026-184 Verification: Events received in Microsoft Sentinel on 2026-07-02. Next review: 2026-09-30
This evidence demonstrates the required lifecycle: a scheduled review, evaluation of logged event types, a reasoned update, and verification that the update worked. An MDR report can support the review by identifying relevant attack patterns or telemetry gaps, but the company should retain the decision record and change evidence.
The contract deserves review as well. Some MDR providers offer log-source onboarding, detection tuning, quarterly security reviews, and recommendations for telemetry improvements. Those services can materially help with the control if the responsibilities are explicit. The organization should still define who approves changes, who performs them, how exceptions are accepted, and where evidence is retained. A provider’s recommendation is not the same as a completed configuration change.
Can MDR contribute to compliance without replacing internal review?
Yes. The strongest model is to use MDR as informed input to the organization’s logged-event review process. MDR analysts see recurring attack techniques, false-positive patterns, missing telemetry, and sources that generate little security value. Their observations can help the company decide to add identity logging, improve endpoint coverage, or stop collecting irrelevant high-volume events. The customer’s designated system owner then evaluates the recommendation, approves the change, verifies implementation, and preserves the record.
This division of responsibility is also financially sensible. The provider supplies specialized monitoring capability that would be expensive to staff internally around the clock. Your organization retains a smaller but essential governance function: periodic decisions about what must be logged to protect CUI, support investigations, and meet NIST SP 800-171 requirements. That function cannot be assumed to exist merely because a vendor has access to alerts.
What is the bottom line for AU.L2-3.3.3?
Verdict: MDR does not replace review for AU.L2-3.3.3, and ordinary manual review of audit records is not, by itself, the practice either. MDR can strengthen security operations and provide valuable recommendations, while the organization must maintain evidence that it periodically reviews its selected logged event types and updates audit configurations when warranted. Treat MDR as a contributor to the process, not as the process owner or the complete compliance answer.
Next step: Ask your IT and MDR leaders to produce one recent audit-event configuration review record, including any resulting change ticket, before approving the next compliance or security-services budget cycle.
