EXECUTIVE BRIEF
National Institute of Standards and Technology Special Publication 800-171A (NIST SP 800-171A) is the assessment companion to NIST SP 800-171, defining how security requirements for protecting Controlled Unclassified Information (CUI) are evaluated in nonfederal systems. For defense contractors, NIST 800-171A plays a critical role in demonstrating compliance readiness, both for internal self-assessments and for external reviews tied to the Department of Defense (DoD), also known as the Department of War, oversight and Cybersecurity Maturity Model Certification (CMMC) requirements.
Dig deeper below to learn how NIST 800-171A assessment procedures work in practice, common high-failure domains, and how organizations can use the standard proactively to assess readiness, strengthen documentation, and improve their overall security posture before formal assessments occur.
What Is NIST 800-171?
NIST 800-171 is a set of cybersecurity guidelines issued by the National Institute of Standards and Technology (NIST) aimed at protecting Controlled Unclassified Information (CUI) in non-federal systems and organizations. It provides 110 security requirements across 14 control families that organizations must implement to safeguard CUI from unauthorized access, disclosure, or theft. NIST 800-171 ensures that companies handling CUI are securing their systems to the highest standards.
For companies working with the U.S. government, especially the Department of Defense (DoD), compliance with NIST 800-171 is often mandatory. The Defense Federal Acquisition Regulation Supplement (DFARS) Clause 252.204-7012 requires defense contractors to implement NIST 800-171 controls to safeguard CUI and report any cybersecurity incidents.
In addition, the requirements in NIST 800-171 form the basis for the Cybersecurity Maturity Model Certification (CMMC). Contractors seeking CMMC Level 2 certification, for instance, must fully implement all 110 security requirements from NIST 800-171. This makes it a key component in preparing for CMMC certification, which will soon be necessary for nearly all defense contractors.
What Is NIST 800-171A?
NIST 800-171A is a supplemental document to NIST Special Publication 800-171. It provides guidelines for assessing the implementation of the security controls specified in that publication. NIST 800-171A explains in detail how organizations should measure their compliance with each control under NIST 800-171, facilitating audits, self-assessments, and preparation for official assessments like CMMC certifications.
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The Difference Between NIST 800-171 and NIST 800-171A
The difference between NIST 800-171 and NIST 800-171A lies in their purpose:
- NIST SP 800-171 is the core framework that outlines security requirements for protecting CUI in non-federal systems and organizations. It provides specific security practices and guidelines that organizations must follow to safeguard this information, focusing on things like access control, incident response, and system security.
- NIST SP 800-171A is a companion document that establishes specific assessment objectives and methods for testing the implementation of each security requirement in NIST 800-171. Essentially, it’s a practical guide for evaluating compliance with NIST 800-171 requirements.
In short:
- NIST 800-171 tells you what to do to protect CUI.
- NIST 800-171A tells you how to assess if you're doing it correctly.
How NIST 800-171A Relates to CMMC
CMMC Level 2 (and some parts of Level 3) is closely aligned with the security requirements in NIST 800-171. Defense contractors working with CUI must comply with these controls to meet CMMC Level 2 certification. NIST 800-171A is therefore foundational to CMMC because it provides the assessment methodology for evaluating compliance with those security controls.
Think of it like this: If NIST 800-171 is the textbook, NIST 800-171A is the study guide, and CMMC is the test.
Organizations seeking CMMC certification can use NIST 800-171A to conduct self-assessments and prepare for official audits. It helps ensure that the required controls are not only in place but also functioning as intended, which is a core requirement for passing a CMMC assessment.
Who Needs To Be NIST Compliant?
If your business is part of the Defense Industrial Base (DIB) and handles CUI or FCI (Federal Contract Information), you’ll need to be CMMC certified. NIST 800-171A sets three assessment levels: Basic, Intermediate, and Advanced (or, as they’re referred to in the CMMC process, Level 1, Level 2, and Level 3). The level of security your business needs depends on the sensitivity of the information you're working with and the specific requirements of your contract(s).
The Anatomy of a NIST 800-171A Assessment Procedure
Each NIST 800-171A assessment procedure follows a consistent assessment method built around three core techniques:
- Examine: Assessors examine your System Security Plan (SSP), policies, configurations, and other documentation.
- Interview: They interview authorized users and administrators to validate implementation.
- Test: Assessors test technical controls like authentication mechanisms or configuration management settings.
Each assessment objective maps back to the SSP and should be supported by evidence. If a requirement isn’t fully met, the assessment outcome informs a plan of action, documenting gaps, remediation steps, and timelines. Importantly, NIST 800-171A also references supplemental material to clarify intent, helping organizations interpret how a control should function in real operating environments.
Key Domains and High-Failure Points
While all assessment procedures matter, some domains consistently represent high-failure points during NIST 800-171A assessments, especially for organizations preparing for their first formal risk assessment.
One of the most common gaps appears in authentication and access control, particularly around defining and enforcing authorized users and ensuring credentials are managed consistently across systems. Weak identity governance often exposes downstream vulnerabilities, even when other technical controls are in place.
Another frequent issue is configuration management. Organizations may have security tools deployed but lack documented baselines or change controls that tie back to their system security plan. Without clear configuration standards, it becomes difficult to demonstrate control effectiveness during a security assessment.
CUI handling also creates challenges. Many organizations struggle to clearly define where CUI resides, maintain an accurate CUI registry, or demonstrate how the confidentiality of CUI is preserved across systems, users, and workflows. These gaps are especially visible when CUI is shared with subcontractors or moves through the supply chain, where responsibility boundaries are often unclear.
Finally, SSP quality itself is a major differentiator. An incomplete or outdated SSP, especially one copied from a generic template without tailoring, makes it difficult to show alignment between documented intent and actual implementation. Assessors are evaluating not just presence of controls, but coherence across documentation, technology, and operations.
How to Use NIST 800-171A for Internal Readiness
NIST 800-171A provides a practical framework for assessing your internal readiness before engaging a third party or undergoing a formal assessment. You can use NIST 800-171A to evaluate current controls, identify gaps, and turn assessment findings into actionable next steps.
Start by aligning your SSP directly to the assessment objectives in NIST 800-171A. For each control, you should verify that the SSP describes how the requirement is implemented, where evidence exists, and who is responsible. This approach turns the SSP into a living operational document rather than a static compliance artifact.
Next, conduct internal exercises using the same assessment method described above: examine, interview, and test. This process often reveals discrepancies between policy and practice, particularly in areas like authentication, CUI handling, and configuration management.
Incorporate any gaps you uncover into a plan of action, prioritized based on risk and potential impact to CUI. This process strengthens your overall risk assessment practices and supports continuous improvement rather than last-minute remediation.
Finally, organizations should evaluate how CUI moves beyond internal systems, especially across subcontractors and the broader supply chain. Internal readiness depends not only on internal controls, but on ensuring partners handling CUI meet the same expectations required of nonfederal organizations supporting the federal government.
Work with ISI to Master Your NIST 800-171 Compliance Needs
At ISI, we understand the challenges of cybersecurity compliance, and we’re here to support you every step of the way. We believe that continuous cybersecurity maturity is more than a compliance necessity: it can help you achieve true operational excellence and allow you to shine with your government customers.
With over 300 years of combined industrial security experience and three Registered Practitioners on our team, our team of experts offers comprehensive support to organizations in all stages of the CMMC assessment readiness process. Through cost effective guidance, expert vendor management, streamlined assessment preparation, and reliable IT and cybersecurity support, we’ll push you over the finish line.
Contact ISI today to find out how we can assist you in achieving and maintaining your compliance goals.
FAQs about NIST 800-171A
Is CMMC Replacing NIST 800-171?
No. CMMC doesn’t replace NIST 800-171; it builds on it.
While NIST SP 800-171 defines the security requirements for protecting CUI in nonfederal systems, CMMC adds a formal accountability and verification layer on top of those requirements. In other words, CMMC defines how compliance with NIST 800-171 is assessed, validated, and enforced.
For most defense contractors, especially those handling CUI, CMMC Level 2 is directly based on NIST 800-171. That means organizations are still implementing the same underlying requirements,they are simply being required to prove compliance through standardized assessments rather than self-attestation alone.
Is NIST 800-171 Mandatory?
Yes, NIST 800-171 becomes a mandatory, binding requirement when it’s incorporated into a contract, typically through DFARS clauses such as 252.204-7012. However, it’s important to note that NIST 800-171 isn’t a law that applies universally to all organizations. It’s a contractual obligation that applies to defense contractors and subcontractors working with CUI. With the rollout of CMMC, enforcement of these requirements is becoming more structured; but the obligation to meet NIST 800-171 itself has existed for years and remains foundational.
What Is the Passing Score for NIST 800-171?
There is no official “passing score” for NIST 800-171 itself. NIST SP 800-171 doesn’t define a pass/fail threshold or certification outcome. Historically, compliance was based on whether an organization had implemented the required controls and documented any gaps in their SSP and POA&M.
That said, scoring becomes relevant when NIST 800-171 is assessed under other programs. For example, under the DoD Assessment Methodology, NIST 800-171 compliance is scored according to the 110 security controls in its framework. Each security requirement represents a single point: the highest score possible on a NIST 800-171 DoD assessment is 110 and the lowest is -203. What qualifies as a passing score depends on the specifics of your contract with the DoD. Some contracts may require a perfect score, whereas others may allow lower scores.
What Are NIST Controls and How Many Controls Are There in NIST 800-171?
NIST “controls” are specific security requirements or practices designed to protect information systems and data from cybersecurity threats. There are 110 controls in NIST 800-171a rev2 that are divided into 14 families, such as access control, incident response, and system protection. Compliance with all 110 of these controls is crucial for defense contractors seeking Level 2 CMMC compliance.
How does ISI help defense contractors achieve and maintain NIST SP 800-171 compliance?
ISI helps defense contractors meet and maintain NIST 800-171 requirements through a purpose-built, end-to-end compliance program. We begin with a detailed gap assessment, then support remediation by deploying the right controls, policies, and security tools to align with CMMC Level 2 and DFARS 7012 expectations. We also streamline required documentation (including SSPs, POA&Ms) and provide continuous monitoring through our integrated IT, cybersecurity, and compliance services.
What tools does ISI provide to assist with mapping and tracking NIST SP 800-171 controls across teams?
ISI provides Security Control, a purpose-built compliance management platform designed for defense contractors. It includes pre-mapped NIST 800-171 controls, role-based assignments, automated tasks and reminders, and a centralized evidence repository for SSP and POA&M updates. The platform also tracks SPRS scoring, control completion, and audit readiness in real time. Combined with managed IT, cybersecurity, and compliance services, it gives teams a clear, organized way to collaborate on every requirement and maintain continuous NIST 800-171 compliance.
How Long Does It Take to Get NIST Certification?
Technically, there is no official NIST certification for NIST 800-171; that’s what CMMC is for. For companies aiming to meet CMMC Level 2 requirements, which align with NIST 800-171, the process may take anywhere from a few months to over a year, based on the organization's initial readiness, the scope of necessary improvements, and the time it takes to find a third-party assessor.
What's the Difference Between NIST 800-171 and NIST 800-172?
NIST 800-172 is an enhanced supplement to 800-171, offering additional advanced security controls to protect high-value assets and critical programs from more sophisticated cyber threats, such as nation-state actors. While 800-171 is widely applicable, 800-172 is used in CMMC Level 3 and other environments requiring higher levels of protection due to the sensitivity of the information.
What's the Difference Between NIST 800-171 and ISO 27001?
NIST 800-171 is a U.S.-specific standard for protecting CUI in organizations working with the U.S. government. ISO 27001 is an international standard for establishing, implementing, and maintaining an Information Security Management System (ISMS). It’s broader and applies to any organization worldwide, offering a framework for managing information security risks across organizations.
While both aim to protect sensitive data, NIST 800-171 is more prescriptive with its controls and limited in its application, whereas ISO 27001 is a global standard focused on risk management and continuous improvement across industries.
Does NIST 800-171 Require FedRAMP?
NIST 800-171 focuses on protecting CUI in non-federal systems, while FedRAMP (the Federal Risk and Authorization Management Program) applies to cloud service providers offering services to federal agencies.
However, if a private contractor uses a cloud service to store or process CUI, the cloud provider may need to be FedRAMP-authorized (or FredRAMP Moderate Baseline equivalent) to comply with NIST 800-171 regulations, since FedRAMP ensures that cloud services meet federal security standards.
