Put simply, if you’re handling CUI and don’t have a living, detailed SSP, your organization is out of compliance and exposed to both contractual and cybersecurity risk. 

Who Needs a System Security Plan? 

If your organization creates, receives, stores, processes, or transmits CUI on behalf of the DoD or another federal agency, you need an SSP. This includes: 

• Prime contractors and subcontractors 
• Managed service providers (MSPs) supporting DoD contractors 
• Technology, engineering, logistics, and manufacturing companies working on defense-related projects 

Even if your team outsources cybersecurity to an MSSP like MAD Security, the responsibility for documentation and compliance still belongs to you. That’s why it's essential to understand what goes into the SSP and how to maintain it. 

Foundations of an Effective SSP  

Creating a System Security Plan isn’t just about filling out a document. It’s about clearly and accurately telling the story of how your organization protects CUI. A strong SSP is clear, detailed, and fully aligned with how your systems and security operations function in real life. 

At MAD Security, we help defense contractors turn this requirement into an opportunity. A well-written SSP can simplify audits and strengthen your cybersecurity posture. That starts with understanding the four qualities every SSP must have. 

The Four C’s: Your SSP Quality Checklist 

A successful SSP must meet four key standards. If any of these are missing, your plan will likely be flagged during a CMMC assessment. 

	Clear  Use straightforward language. Avoid vague terms like “handled appropriately” or “in accordance with policy” unless you explain what that means. An assessor should be able to read about your implementation and understand exactly how the control is applied in your environment.
	Concise Stay focused. Each control should explain only what’s necessary: who does what, how it’s done, when it happens, and with what tools or processes. Long-winded descriptions or policy copy-paste sections are red flags for assessors.
	Consistent Use the same terminology throughout. If you refer to “XYZ System” in one place, don’t call it “production environment” or “network A” elsewhere. Keep role names, control statuses, and system identifiers consistent across all controls and references.
	Complete Every single control and its related assessment objectives (from NIST SP 800-171A) must be answered. If a control includes parts A, B, and C, you must describe each part. Leave no blank sections. If you must use “N/A,” back it up with a detailed, risk-based justification.

Telling the Story: Who, What, When, and How 

Think of your SSP as a narrative. It’s not enough to say that a control is “in place.” You need to show that it’s implemented by explaining:

This storytelling model isn’t just helpful. It is required. NIST SP 800-171A and CMMC assessment guides emphasize that controls must be described in a way that makes them testable and traceable to evidence. 

A vague or generic SSP may look like progress, but it won’t hold up under a real CMMC Level 2 assessment. That’s why MAD Security encourages you to build your SSP with the same mindset you bring to engineering, quality assurance, or operations: clarity, precision, and accountability. 

Required Structure of the CMMC SSP 

A System Security Plan is not a generic document. It must be tailored to your environment, reflect your actual security posture, and follow a structured format that ensures nothing is overlooked. Assessors do not just look for whether you have an SSP. They look to see whether it accurately represents your systems, boundaries, and control implementations. 

At MAD Security, we recommend building your SSP using a format that draws from the NIST SP 800-18 framework. This structure should be adapted specifically for NIST SP 800-171 and the related CMMC Level 2 assessment requirements. 

Core System Plan Elements  

To meet CMMC expectations, your SSP should contain the following core elements. These define the scope, ownership, and supporting documentation that make your plan defensible during an audit. 

Required Content in a CMMC Context 

CMMC assessments are based not only on technical implementations but also on how well your documentation supports compliance. The content of your SSP must align with how your systems operate in real life and how they are governed under your contract. 

When your SSP includes all of these elements and uses clear language to describe your system's architecture, responsibilities, and scope, you are building a document that can stand up to scrutiny. A strong structure makes your control implementations easier to write, easier to verify, and easier to maintain. 

Control-by-Control Implementation Strategy 

At the heart of your SSP is how you explain each control. For CMMC Level 2, assessors will evaluate how well your organization has implemented the 110 security requirements defined in NIST SP 800-171. To prepare for this, your SSP must align directly with the assessment objectives in NIST SP 800-171A. 

A Control-Writing Framework That Works  

Each control must be documented in a way that allows an assessor to understand what you do, how you do it, and who is responsible. MAD Security uses a simple but powerful framework to help clients build implementation descriptions that meet these expectations: 

Example: Writing an Effective Response for AC. L2-3.1.1 

Control: Limit system access to authorized users, processes acting on behalf of authorized users and devices (including other systems). 

A weak response: “User access is controlled based on policy.” 

A strong response: “The system administrator provisions user accounts through Active Directory after written approval from department managers. Access requests are submitted through our IT ticketing system, which tracks requestor, justification, and approver. Access is granted only to users with a business need, based on the least privilege. The security team reviews account activity quarterly. Evidence includes account request forms, Active Directory group listings, and quarterly access review reports.” 

This type of response is what assessors expect. It is testable, verifiable, and linked to real-world procedures and artifacts. 

Control Status and Responsibility Labels 

Each control in your SSP should include a status label and a clear explanation of who is responsible. Use the following labels consistently: 

If a control is hybrid or inherited, your SSP must explain the division of responsibility. Use a simple table or Shared Responsibility Matrix if needed. Assessors will want to know who does what they do. 

Write for Evidence and Assessment  

Every control implementation should be written with two goals:

1. Tell the truth about your current situation

Do not document an ideal future. Your SSP must reflect on what is being implemented now. 

2. Make it easy for an assessor to test

Your implementation descriptions should naturally lead to evidence, such as policies, screenshots, logs, or system settings. 

Ask yourself: If someone asked me to prove this control is in place, could I hand them something right now? 

When each control is treated as a mini case study of how your security program works, your SSP becomes a powerful tool. It is no longer just a requirement. It becomes documentation that supports audit readiness, internal training, and ongoing system improvement. 

Shared Responsibilities and Third-Party Support

Many defense contractors rely on outside partners to help manage or implement security controls. Whether it’s a Managed Security Service Provider (MSSP) like MAD Security, a cloud provider, or an internal IT support company, those relationships must be documented in your SSP. 

In a CMMC assessment, it is not enough to say that a third party “handles security.” Your SSP must explain exactly which parts of each control are your responsibility and which are managed by others. 

Hybrid Controls Are Common and Must Be Explained 

Most SSPs in the DIB environment include hybrid controls. These are controls where implementation is split between your organization and one or more external providers. 

For example, MAD Security might handle 24/7 log monitoring and threat detection for your systems. But your internal IT team is still responsible for user account creation, role assignment, and onboarding. That’s a hybrid model, and the SSP needs to spell it out clearly. 

Every control that involves outside support should include: 

• A clear description of the third-party relationship 
• Identification of who performs which task 
• A summary of how responsibilities are verified or managed 

If a control is fully inherited from a provider, such as through a FedRAMP-authorized cloud service, your SSP should include references to documentation from that provider. You are still responsible for understanding what they cover and showing how it supports your compliance. 

Use a Shared Responsibility Matrix  

One of the most effective ways to clarify hybrid implementations is by including a Shared Responsibility Matrix in your SSP or as an appendix. This table helps assessors quickly see how responsibilities are divided across all relevant controls. 

Your matrix should include: 

• The control number (e.g., AC. L2-3.1.1) 
• A summary of the control activity (e.g., “Limit system access to authorized users”)
• Your organization’s responsibility
• The provider’s responsibility 
• Evidence or reference documents 

This type of clarity builds confidence with assessors. It also helps your internal teams and vendors stay aligned on who is doing what and when. 

Documenting and Verifying Third-Party Services 

When you rely on a third party for any part of your security implementation, your SSP must do more than just name the provider. You should also: 

• Describe the scope of services they provide (e.g., managed detection and response, vulnerability scanning) 
• Identify how you verify those services (e.g., monthly reporting, audit logs, service-level agreements) 
• Reference supporting documentation, such as signed agreements or onboarding records 

If MAD Security is part of your cybersecurity program, your SSP should reflect the operational reality of that relationship. That includes how our tools are deployed, what roles we play in control implementation, and how you track the effectiveness of our support. 

Clear documentation of shared responsibilities helps you pass your audit. But more importantly, it helps ensure that your cybersecurity program is not just functional. It is accountable, measurable, and resilient. 

Writing and Maintenance Best Practices 

Writing a strong System Security Plan is not a one-time task. It requires coordination, clarity, and regular upkeep. In many cases, SSPs fail assessments not because a control is missing, but because the documentation is unclear, incomplete, or out of sync with actual operations. 

Use Clear, Actionable Language 

When describing how a control is implemented, avoid vague or passive statements. Use an active voice and focus on what your organization does. 

Instead of saying, "Access is granted based on need." 

Write: "The IT administrator grants access only after receiving written approval through the access request workflow. Requests are logged and retained in the ticketing system for 90 days." 

Avoid these common mistakes: 

• Copying language directly from the control requirement without explanation
• Referencing a policy without describing what is done 
• Using terms like “regularly,” “appropriately,” or “securely” without defining what that means 

Each control should read a brief, focused summary of your real implementation, what it does, when it happens, how it happens, and where the evidence can be found. 

Match the SSP to Your Operational Reality 

Your SSP must reflect how your systems and teams work. Assessors will check that your documentation lines up with evidence, such as logs, access control records, or user training reports. 

To ensure alignment: 

• Use the same names and labels for systems, roles, and tools throughout the SSP 
• Review your network diagrams and inventory lists to confirm they match what is described 
• Coordinate with your service providers to ensure shared controls are accurately described 

If your SSP says a control is “implemented,” be ready to show how and by whom. 

Keep the SSP Updated as a Living Document  

CMMC assessments, DFARS audits, and even internal reviews all require that your SSP is current. This means the SSP should be reviewed and updated: 

• At least once per year 
• Any time a major change occurs in your system or environment (such as infrastructure migration, tool replacement, or personnel changes)
• After an incident or as part of a corrective action 

Maintaining a change log within the SSP is recommended. This log should note the date of each update, a summary of what changed, and who approved the revision. This demonstrates to assessors that your SSP is not just a formality. It is an integral part of your cybersecurity program. 

Clear, current, and consistent documentation is a major differentiator during assessments. A well-written SSP tells the story of a well-managed system. With MAD Security’s guidance and services, our clients gain not just implementation support but also the documentation and structure needed to prove it. 

Monitoring and Lifecycle Integration  

An effective System Security Plan is not just documentation. It is part of your ongoing cybersecurity lifecycle. For defense contractors pursuing CMMC Level 2 compliance, the SSP must reflect more than their control implementations at a single point in time. It should show how your program adapts, responds, and improves. 

Treat the SSP as a Living Document 

The SSP should evolve alongside your environment. Systems change. Tools are replaced. Responsibilities shift. A static SSP quickly becomes a liability. 

You should review and update your SSP:

• At least annually 
• Whenever there is a system or control change 
• After significant personnel transitions 
• Following a security incident or audit finding 

Build this into your normal operational rhythm. Schedule periodic reviews and link them to your internal change management process. Include a change log in the SSP that tracks when updates were made, who made them, and what changed. 

Connect the SSP to Your Security Operations 

The more your SSP reflects real operations, the easier it is to maintain. If you are using a managed detection and response (MDR) service, vulnerability management platform, or cloud-based compliance tool, your SSP should reference those tools directly. 

You can tie your SSP to: 

• Ticketing systems for access control and incident response workflows 
• Monitoring platforms that generate alerts and logs 
• Policy documents that govern configuration changes or patching schedules
• Service-level reports from your MSSP, such as monthly detection summaries 

This shows assessors that your controls are not just documented. They are also active, monitored, and measured. 

Automate Where Appropriate 

Many organizations use tools like Microsoft Purview Compliance Manager, GRC platforms, or audit dashboards to track control status and evidence. If you use automation to manage SSP-related tasks, describe them in your documentation. 

For example: “User access requests and approvals are logged through the ServiceDesk Plus platform. Reports are generated monthly and reviewed by the IT manager.” 

Automation is not required for CMMC, but assessors will want to understand how you maintain consistency and oversight. Even simple automation, such as alerting when policies are overdue for review, can strengthen your SSP’s credibility. 

When the SSP is embedded into your organization’s operations, it becomes more than a requirement. It becomes a reflection of a mature cybersecurity program. MAD Security helps clients align people, processes, and tools, so their SSP stays accurate, defensible, and audit-ready always. 

Tools, Templates, and Resources 

Your System Security Plan is only as strong as the tools, references, and structure behind it. Many defense contractors struggle not because they lack technical controls, but because they lack the documentation support to properly describe and defend those controls. 

Templates for SSP Development 

Having a structured starting point can make a significant difference. MAD Security provides clients with SSP templates that are built around best practices, clear formatting, and alignment with CMMC requirements. 

Templates we recommend include: 

These templates are designed to simplify SSP development and support consistent documentation across all control families. 

Recommended Tools for Documentation and Evidence Tracking 

Many organizations benefit from basic tooling to maintain their SSP and related documentation. These tools can help you track changes, link controls to evidence, and prepare audits. 

Examples include: 

• Document version control systems (such as SharePoint, Confluence, or Google Workspace) 
• Ticketing and workflow tools (such as Jira, ServiceNow, or Spiceworks) 
• Compliance tracking platforms (such as Microsoft Purview Compliance Manager or other GRC solutions) 

If you use automation to track control status or monitor compliance, your SSP should reference that. The goal is to show that your documentation is current, verifiable, and connected to real-world processes. 

Authoritative References  

Use the following resources to ensure your SSP aligns with government expectations and assessment criteria: 

With the right structure, supporting tools, and trusted references, your SSP becomes more than just a compliance document. It becomes a living record of your cybersecurity program’s integrity and maturity. MAD Security helps clients connect these resources into a unified documentation strategy that stands up to scrutiny. 

Final Notes and Recommendations 

Writing and maintaining a System Security Plan is one of the most important steps in achieving and sustaining CMMC Level 2 compliance. It is not just paperwork exercise. Your SSP is the foundation for documenting how your organization protects CUI and meets its contractual and regulatory obligations. 

Throughout this guide, we have emphasized one consistent message. A strong SSP reflects how your system operates in real life. It connects technical controls, organizational processes, and third-party support into a clear, accurate, and audit-ready document. 

Why SSPs Fail and How to Get It Right   

Many SSPs fall short during assessments for the same reasons: 

• Control implementations are vague or copied from policy 
• Shared responsibilities are unclear or undocumented 
• References to policies and systems are inconsistent
• The plan is outdated or no longer reflects the actual environment 

These are avoidable mistakes. With the right structure and support, your SSP can become a competitive advantage. It can reduce audit delays, improve team alignment, and strengthen your cybersecurity skills. 

The MAD Security Advantage 

MAD Security helps defense contractors move from guesswork to clarity. We bring deep experience across NIST, DFARS, and CMMC requirements, along with practical insight from supporting Joint Surveillance Voluntary Assessments and CMMC readiness efforts. 

We support our clients with: 

• Proven SSP templates and documentation frameworks 
• Shared responsibility modeling for MSSP and hybrid environments 
• Guidance on aligning technical controls with assessment objectives 
• Documentation reviews mapped directly to NIST SP 800-171A 
• 24/7 security operations and monitoring that support evidence collection and continuous compliance 

When you work with MAD Security, you are not just hiring a vendor. You are gaining a long-term partner committed to your success.

Sustaining Your SSP Long Term  

Once your SSP is built, the work does not stop. Keep it current. Tie it to real operations. Use it to train your team and guide internal audits. Treat it as a living document that reflects the strength and integrity of your cybersecurity program. 

If you need help building, reviewing, or improving your SSP, MAD Security is ready to support you. Our team works alongside yours to simplify compliance, strengthen documentation, and help you achieve CMMC with confidence. 

Frequently Asked Questions (FAQs)  

Original Publish Date: July 10, 2025

By: MAD Security