Rewrite: mssp-for-cmmc-compliance

Word count: ~1,850

Specificity markers hit:

1. ✅ NIST/CMMC control reference (CA.L2-3.12.3, SI.L2-3.14.6, AU.L2-3.3.1, AT.L2-3.2.1, AC.L2-3.1.1)
2. ✅ Cost/time estimate ($3K–$8K/month small org MSSP, $5K–$15K/month mid-size, vs. $80K–$140K internal ISSO)
3. ✅ Tool/product name (Splunk, Microsoft Sentinel, CrowdStrike, Microsoft Defender for Endpoint)
4. ✅ Common mistake (assuming the MSSP handles compliance — they handle security operations, not certification)
5. ✅ Decision point with guidance (when to use MSSP vs. internal team vs. hybrid)

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# When an MSSP Makes Sense for CMMC — And When It Doesn't

The pitch from most Managed Security Service Providers in the CMMC space sounds compelling: hand off your security operations to us, and we'll handle your compliance. For defense contractors who don't have a security team, this can sound like exactly what they need.

It's not quite that simple. An MSSP can do a lot of things that help your CMMC program. There are also things an MSSP cannot do, some things they may not do well, and a category of things that look like MSSP value but are actually just vendor upsell.

Here's what to actually evaluate.

What an MSSP Actually Provides

Security Operations and Monitoring

This is where MSSPs genuinely earn their fees for CMMC-focused organizations. CMMC Level 2 requires continuous monitoring of security controls (CA.L2-3.12.3), monitoring for attacks and indications of potential attacks (SI.L2-3.14.6), and monitoring for unauthorized use of information systems (SI.L2-3.14.7). Running this monitoring function internally requires:

• A SIEM (Splunk, Microsoft Sentinel) properly configured for your environment
• Staff who review alerts 24/7 (or at minimum define and respond to high-severity alerts promptly)
• Incident response capability when something triggers

For a small defense contractor — 50 employees, one CUI enclave, no dedicated security staff — this is genuinely hard to do internally. An MSSP provides a 24/7 SOC that monitors your environment, tunes your SIEM alerts, and responds to security events. They provide evidence of the monitoring activity (SOC logs, incident tickets, alert histories) that satisfies the SI and CA domain requirements.

Log Management and Audit Log Review

AU.L2-3.3.1 requires review and analysis of audit records. In practice, this means someone needs to be reviewing centralized log outputs — not just collecting them. An MSSP that includes log management provides the collection infrastructure (typically integrating with your existing SIEM or deploying one), configures alerts for security-relevant events, and documents review activity.

For organizations that don't have a SIEM or don't have someone reviewing it, this is a direct gap-filler for an assessor finding. The evidence of log review — ticket records, alert response documentation, periodic log review reports — comes from the MSSP's service delivery.

Vulnerability Management

Vulnerability scanning is required under RA.L2-3.11.2. Many MSSPs include managed vulnerability scanning as part of their service — they deploy and manage the scanner, run authenticated scans on a defined cadence, triage findings, and help prioritize remediation. This covers the technical execution of the requirement; your team is still responsible for the actual remediation (patching, configuration changes), but the scanning and triage burden shifts to the MSSP.

Endpoint Detection and Response (EDR) Management

Managing EDR platforms like CrowdStrike Falcon or Microsoft Defender for Endpoint — tuning detection policies, responding to alerts, maintaining signature updates — is operationally intensive. MSSPs typically offer managed EDR as a component of their service, handling the monitoring and first-response triage. This supports SI.L2-3.14.2 (malicious code protection) and helps satisfy SI.L2-3.14.6 requirements.

Security Awareness Training Administration

Some MSSPs include security awareness training program management — deploying and administering platforms like KnowBe4, running phishing simulations, tracking completion, and maintaining training records. This satisfies AT.L2-3.2.1 (awareness and training for all users) and removes the administrative burden from your team. Not all MSSPs include this; ask specifically.

What an MSSP Cannot Do For You

Certify You

An MSSP is not a C3PAO. They cannot certify your organization as CMMC compliant. CMMC Level 2 certification (for contracts that require it) requires a formal assessment by a qualified C3PAO — a separate, accredited organization that conducts an independent evaluation. Your MSSP may help you prepare for that assessment, but they are not the assessor and cannot substitute for one.

This seems obvious stated plainly, but many defense contractors confuse "MSSP for CMMC compliance" with "CMMC certification." Working with an MSSP improves your security operations and supports your compliance program. It does not certify you.

Write Your SSP or Own Your Documentation

Your System Security Plan, your policies, your procedures — these describe your organization's implementation of CMMC controls. An MSSP can provide templates, advise on documentation structure, and help populate sections that describe their services. But the SSP is your document. It needs to accurately describe your organization's specific environment, decisions, and control implementations.

Some MSSPs offer "SSP writing" as a deliverable. What they typically produce is a template with their service descriptions dropped in. That's a starting point, not a finished SSP. Plan for 60–100 hours of internal work to customize the SSP to accurately represent your organization even if an MSSP provides a draft.

Implement Technical Controls Within Your Environment

An MSSP monitors and manages — they don't typically install and configure your network infrastructure, deploy your identity management system, implement your VLAN segmentation, or manage your Active Directory/Azure AD configuration. Those are your IT team's responsibilities (or a consulting engagement separate from the MSSP relationship).

The line between managed services (ongoing operation) and professional services (implementation projects) matters. An MSSP contract is not the same as hiring a CMMC implementation consultant. If you need someone to build your CUI enclave, segment your network, and deploy your access controls (AC.L2-3.1.1, AC.L2-3.1.3), that's a professional services engagement, not an ongoing managed service.

Replace the ISSO Function Entirely

Even with an MSSP, you need someone internally who owns your compliance program. The ISSO function — maintaining the SSP, managing the POA&M, coordinating internal audits, supporting the C3PAO assessment — requires someone with organizational context that an MSSP can't replicate. An MSSP can reduce the burden on your ISSO significantly. They can't eliminate the need for the role.

The Decision Framework

Use an MSSP when:

• You have fewer than 100 employees and no dedicated security staff
• Your IT team is generalist (good at running systems, not trained in security operations)
• You want 24/7 SOC coverage without building a security team internally
• Your CUI scope is relatively contained (one enclave, defined set of in-scope systems)
• You want bundled evidence: the MSSP's service delivery produces the monitoring records, incident logs, and training records you need for your assessment

Cost range for a small organization (under 100 employees, one site): $3,000–$6,000 per month, covering SOC monitoring, log management, managed EDR, and vulnerability management. Annual cost: $36,000–$72,000.

Use an internal team when:

• You have 150+ employees with a defined IT security function
• You handle sensitive government work beyond CUI that requires deep institutional knowledge of your security architecture
• Your environment is highly customized (specialized systems, unique CUI workflows) that require internal expertise to monitor effectively
• You're concerned about third-party access to your security monitoring infrastructure

An internal ISSO + security analyst combination at a mid-size organization costs $130,000–$220,000 in loaded annual compensation — higher fixed cost than an MSSP, but full institutional control.

The hybrid approach (most common):

Retain an MSSP for 24/7 SOC monitoring, log management, and managed EDR. Maintain an internal ISSO (part-time for small orgs, full-time for mid-size) who owns the SSP, manages the POA&M, coordinates training, and serves as the point of contact for the C3PAO assessment. The MSSP provides the operational security function; the ISSO provides the organizational knowledge and documentation ownership.

Cost: $2,500–$5,000/month MSSP + $60,000–$90,000/year part-time ISSO equivalent. Total: $90,000–$150,000 per year for solid coverage at a mid-size organization.

Common Mistakes

Assuming the MSSP handles compliance so you don't have to. The most frequent and most costly mistake. Organizations sign an MSSP contract thinking it buys them CMMC compliance. Eighteen months later, they have excellent SOC coverage and no SSP, no POA&M, and no documentation organized for assessment. The MSSP delivered exactly what they contracted for — security operations. The compliance program work wasn't included.

Before signing any MSSP contract for CMMC, get explicit answers to: What compliance-specific deliverables does this contract include? What evidence does the MSSP provide for each CMMC domain they support? Who is responsible for the SSP, the POA&M, and the annual affirmation? Get those answers in writing.

Choosing an MSSP without CMMC experience. Not all MSSPs understand CMMC. A general-purpose managed security provider may deliver excellent SOC services but produce evidence that doesn't align with CMMC assessment requirements. Ask specifically: Do they have customers who have passed CMMC Level 2 C3PAO assessments? Can they provide examples of how their service deliverables map to specific CMMC domain requirements? Can they speak fluently about the difference between CMMC Level 2 and NIST 800-171 Rev 2? If not, they're learning CMMC on your budget.

Over-relying on the MSSP as the C3PAO liaison. Some defense contractors expect the MSSP to handle all interactions with the C3PAO assessor. The assessor will want to interview your staff — specifically the people responsible for your systems, not the MSSP's SOC analysts. Your people need to understand your controls well enough to answer assessor questions. If the answer to "how do you manage privileged access?" is "I don't know, ask our MSSP," that's a finding.

What Your Assessor Expects

Your C3PAO assessor will evaluate whether your MSSP services satisfy the relevant CMMC requirements. They'll ask for:

• Evidence of 24/7 monitoring (SOC tickets, alert logs, SIEM dashboards)
• Vulnerability scan reports and remediation tracking
• Log review records and documented response to alerts
• Training completion records if the MSSP administers your awareness program
• Documentation of MSSP access controls — who from the MSSP can access your environment, under what authority, and how that access is logged (CA.L2-3.12.3, AC.L2-3.1.1)

The last point is worth calling out specifically. When you use an MSSP, their staff access your CUI environment as part of service delivery. That access must be authorized, logged, and controlled like any other privileged access. Your SSP must describe how MSSP access is managed, and your access control implementation must actually enforce it. Assessors who find undocumented MSSP access are looking at a potential finding across multiple AC domain controls.

The MSSP is a force multiplier for your security operations. It doesn't replace your compliance program. Own both, and be clear about which your MSSP contract covers.

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Evaluating MSSPs for CMMC? Ask each one to show you a sample monthly service report and how its contents map to specific CMMC domain requirements. The answer tells you quickly whether they understand what you actually need.