If you're new to NIST Special Publication 800-53, understanding the role of security assessments is critical for managing risks and maintaining compliance. Unlike some frameworks, NIST SP 800-53 isn’t a certifiable standard, meaning there’s no official “NIST 800-53 certification.” However, security assessments can be done and still play a crucial role in ensuring your controls function as intended, identifying vulnerabilities, and meeting regulatory requirements.

Whether your organization conducts internal assessments or works with third-party auditors or professional auditors for an attestation, the process should align with your unique risk landscape. Setting the right assessment frequency and scope helps transform security evaluations into actionable insights—strengthening your security posture and building trust with stakeholders.

In this guide, we’ll break down NIST 800-53 Rev 5 security assessment requirements, compare internal vs. external assessments, and walk through the assessment procedure step by step to help you implement an effective assessment strategy.

The CA control family: NIST 800-53 security assessment requirements

NIST 800-53 Rev. 5 dedicates an entire control family, Control Assessment, Authorization, and Monitoring (CA), to the security assessment process. Within this family, CA-2: Control Assessments defines how organizations should evaluate the implementation and effectiveness of their security and privacy controls.

CA-2 requires organizations to conduct regular security assessments, typically at least annually, or more frequently based on the organization’s specific risk profile:

• Federal agencies: Must conduct annual assessments as part of FISMA compliance.
• Private sector organizations: Often conduct assessments or attestations quarterly, biannually, or annually, depending on their risk management strategy and contractual obligations.
• Continuous monitoring: Organizations with a mature security posture often supplement periodic assessments with automated tools for continuous control monitoring to detect and respond to risks in real time.

These assessments focus on ensuring security measures are functioning as intended and are sufficient for addressing evolving risks. NIST 800-53 also emphasizes thorough documentation throughout the assessment process, including creating a Security Assessment Report (SAR) and a Plan of Action and Milestones (POA&M) to track and address any identified vulnerabilities or compliance gaps.

Who can conduct assessments?

One of the unique aspects of CA-2 is its flexibility in who conducts the assessments. While internal teams can lead assessments, the framework specifies that assessors must maintain a level of independence to ensure objectivity. This independence can be achieved internally by assigning a separate team or externally by hiring a third-party auditor.

In addition to its baseline security requirements, CA-2 includes several control enhancements that allow organizations to tailor their assessment processes to their needs. Control enhancements provide additional capabilities or safeguards beyond the standard control. For example, CA-2 enhancements include leveraging automated tools for continuous monitoring, integrating real-time feedback on control performance, and ensuring comprehensive coverage of security and privacy controls, even in complex supply chain scenarios. These enhancements help organizations achieve a more proactive and robust approach to assessments.

Internal vs external security assessments

As mentioned above, organizations have the flexibility to choose between internal assessments, external assessments, or a combination of both. Each approach has its advantages, depending on the organization’s needs and resources.

Internal assessments are typically conducted by the organization’s own security, compliance, or risk management teams. These assessments are often used as a preparatory step, allowing organizations to identify and address gaps before engaging external auditors. Internal assessments are cost-effective and allow for greater control over the process, but they require strong internal expertise and a commitment to objectivity.

External assessments, on the other hand, are conducted by third-party assessors who bring an independent perspective and often greater expertise. These assessments are particularly valuable in high-stakes scenarios, such as demonstrating compliance for federal contracts or meeting regulatory requirements. External assessments also carry more weight with external stakeholders, such as customers or partners, because they offer an unbiased validation of your controls.

Some organizations choose a hybrid approach: starting with an internal assessment to identify and address gaps, followed by an external assessment for validation and to ensure compliance. When deciding which method to use, consider factors like your organization’s internal expertise, budget, and the stakes involved in demonstrating compliance.

If your team is experienced with compliance and/or NIST 800-53 and the assessment is low-stakes (such as for internal process improvements), an internal assessment is sufficient. For high-stakes compliance and/or contract scenarios, lack of expertise, or the need for an unbiased evaluation, hiring external auditors is a better option. A combination of both approaches, internal self-assessments followed by external validation, can often offer the best balance of cost, efficiency, and reliability.

If you’re using compliance automation tools that map NIST 800-53 controls, they can significantly streamline both internal and external assessments. Tools like Secureframe can automate control testing and evidence collection and generate dashboards that help internal teams identify gaps.

How to perform an internal security assessment under NIST SP 800-53 Revision 5

Conducting an internal security assessment might sound overwhelming at first, but breaking it down into clear steps makes it much more manageable. The goal is simple: evaluate your security controls, identify any gaps, and document everything properly to ensure compliance with NIST 800-53 Rev. 5.

It all starts with defining what you’re assessing and ends with documenting any fixes or improvements needed. Along the way, key documents like System Security Plans (SSPs), network diagrams, and risk assessment reports help keep everything organized and on track.

We’ll walk you through each step of the process, covering what you need to do, what documentation is required, and how to stay aligned with NIST 800-53’s information security standards.

Step 1: Define scope

Before diving into testing security controls, you first need to clearly define the scope of your assessment. This step helps you focus your efforts and ensures you're evaluating the right systems and data.

To start, identify all systems and applications that will be part of the assessment. This includes anything that handles sensitive data, interacts with critical infrastructure, or is subject to compliance requirements.

Next, define system boundaries: what’s included in the assessment and what falls outside of it. Be sure to account for external dependencies, such as cloud service providers, third-party vendors, or external APIs, since these can introduce security risks that need to be considered.

There are a few key documents you'll need at this step. First is your SSP, which outlines the security controls you've implemented to mitigate risks and satisfy NIST 800-53 requirements. This document serves as a roadmap for your assessment.

You'll also need to reference your network diagrams, which provide a visual representation of your IT infrastructure and help you see how different systems are connected. Finally, data flow diagrams are crucial for understanding how data moves between systems, applications, and users. These diagrams help identify potential security vulnerabilities, such as weak points where unauthorized access or data leaks could occur.

By the end of this step, you should have a clear picture of what you’re assessing, why, and which documents will guide your evaluation.

Step 2: Perform control assessments

Now that you’ve defined your scope, it’s time to evaluate your security controls. This means checking whether your controls are properly implemented and working as intended.

Start with your SSP, which details the security and privacy controls your organization has put in place. This document acts as a checklist for the assessment, allowing you to systematically go through each control and verify whether it has been effectively implemented and is performing as intended.

Testing controls involves reviewing configuration settings, testing access controls, and analyzing audit logs. For example, if you have multi-factor authentication (MFA) as a security control, you should verify that it is enforced for all relevant systems and users. Or if your security measures include encryption for sensitive data, you’ll need to confirm that encryption is properly configured and functioning as expected.

To document this step, you will need to create a Security Control Assessment (SCA) Plan, which outlines the testing methods, objectives, and expected outcomes for each control being assessed. Record results for each control assessment and include evidence of whether the controls are operating correctly. Additional documentation, such as vulnerability scan reports and audit logs, help to support your findings and ensure a thorough evaluation of system security.

Step 3: Document findings

Once you’ve completed your control assessments, the next step is to compile your findings into formal reports. This is where all your observations, test results, and identified security gaps come together to create a comprehensive picture of your organization’s security posture.

The Security Assessment Report (SAR) is the main document used to summarize assessment findings. It should clearly outline which controls were tested, the results of each test, and whether any weaknesses or compliance gaps were discovered. The SAR should be written in a way that both technical and non-technical stakeholders can understand, providing enough detail to guide remediation efforts.

If any deficiencies were found, they should be documented in your POA&M to detail specific vulnerabilities, their potential impact, and a plan for remediation, including deadlines and assigned responsibilities. The POA&M is your action plan, telling you exactly what needs to be fixed, who is responsible for fixing it, and when it should be completed.

Thorough documentation is crucial at this stage because it provides a historical record of your security posture. It also helps demonstrate due diligence in the event of a compliance audit or regulatory review.

Step 4: Create a remediation plan

Once you’ve documented your findings, it’s time to take action. The goal of this step is to fix any identified weaknesses and ensure security controls are strengthened.

Start by reviewing your POA&M to prioritize remediation efforts. Some issues may be minor configuration fixes, while others may require more extensive changes, such as updating security policies or implementing additional controls. Be sure to assign clear responsibilities to the appropriate team members and set realistic deadlines for completion.

Once fixes have been implemented, controls should be reassessed to confirm that the remediation efforts were successful. This might involve re-running vulnerability scans, reviewing system configurations, or performing follow-up testing.

Step 5: Implement continuous monitoring

To maintain strong security over time, you need a continuous monitoring strategy that ensures controls remain effective as new threats emerge.

A Continuous Monitoring Plan should outline how your organization will track security performance over time. This includes defining which security metrics will be monitored, how frequently assessments will be conducted, and what tools will be used for monitoring. Many organizations use automated monitoring tools to continuously track system security and generate real-time alerts for potential issues.

Step 6: Retain or submit assessment reports

Once the assessment is complete, the final step is determining whether the reports need to be retained internally or submitted to an external entity.

For most private sector organizations, internal security assessments do not need to be submitted externally. However, it is important to retain all of your documentation for future reference, including the SSP, SAR, and POA&M. These documents can be useful for internal security reviews, audits, vendor risk management processes, or customer inquiries.

If your organization is a federal agency or a government contractor, you may be required to submit certain reports as part of FISMA compliance or contractual obligations. In these cases, reports might be shared with oversight bodies, contracting authorities, or third-party auditors.

Even if external submission isn’t required, maintaining these reports ensures you have a documented history of regular security assessments, helping your organization track improvements and demonstrate compliance when needed.

Expert tips for a successful NIST 800-53 security assessment

A well-executed security assessment is about gaining actionable insights into your organization’s security posture, ensuring your controls are both effective and aligned with compliance requirements.

To help you make the most of your assessment process, our team of federal compliance experts and former auditors shared their top strategies for an effective NIST 800-53 security assessment, from streamlining the process and improving collaboration to maintaining compliant documentation.

Automate manual and repetitive tasks

Mapping controls, testing security measures, gathering evidence, and compiling reports are incredibly time-consuming tasks, and doing it all manually increases the risk of errors and inefficiencies. A compliance automation tool can handle a lot of the heavy lifting, reducing the manual effort involved in testing and reporting while providing real-time insights into your security posture. It can also automate evidence collection, keep your documentation organized, and ensure nothing slips through the cracks, making the entire assessment process much smoother.

Prioritize collaboration

Security assessments shouldn’t be a solo mission for a single team. The best results come when IT, compliance, legal, operations, and leadership are all on the same page. Getting input from different teams ensures you’re looking at security from all angles and catching issues that might otherwise be overlooked.

Plus, when everyone is involved from the start, it’s much easier to get buy-in for any remediation efforts later. A more collaborative approach means fewer roadblocks and better alignment across your organization.

Maintain documentation

Don’t let your compliance documents and assessment records sit in a folder collecting dust. As you remediate vulnerabilities, update security policies, or make system changes, your documentation should reflect those updates. Keeping things current ensures you always have an accurate picture of your security posture and makes life easier when it’s time for an audit or external review. It also helps with internal reviews, ensuring that when someone needs to understand the state of your security program, they aren’t working off outdated information.

Leverage continuous monitoring tools

Once-a-year security assessments aren’t enough to stay ahead of emerging threats. Continuous monitoring helps you catch misconfigurations, outdated controls, and new risks before they become major issues.

Ideally, you should have automated monitoring tools in place to track security performance and flag potential vulnerabilities in real time. Even if a full security assessment only happens once a year, quarterly check-ins and ongoing monitoring help you stay proactive rather than reactive.

Cross-map controls

If your organization follows more than one compliance framework, managing separate assessments for each can be a huge headache. Instead of duplicating efforts, map your NIST 800-53 controls to other frameworks like NIST 800-171, CMMC, FedRAMP, TX-RAMP, CJIS, the NIST Cybersecurity Framework, or ISO 27001 to create an integrated compliance strategy. This makes audits and reporting much more efficient, helps reduce redundant work, and ensures you’re covering all your security and regulatory bases without unnecessary complexity.

Making NIST 800-53 assessments faster and more effective

NIST 800-53 security assessments are an essential part of maintaining compliance and protecting your organization’s information systems and sensitive data. While the process can be resource-intensive, automation tools can significantly streamline the assessment process.

Tools like Secureframe simplify tasks like control mapping, evidence collection, and continuous monitoring, reducing the manual overhead and ensuring more accurate and timely assessments. By leveraging automation and following a structured assessment process, organizations can not only meet the requirements of NIST 800-53 but also achieve a stronger, more proactive security posture. Request a demo to see how our platform can help you streamline compliance and strengthen your security practices.