Access Control 3.1.5 (3.1.5)
Employ the principle of least privilege, including for specific security functions and privileged accounts.
Get Full GuidanceWhat Is This CMMC Control?
This control requires organizations to give users and systems only the minimum access rights they need to do their jobs—nothing more. This applies to both regular users and privileged accounts like administrators. The goal is to reduce risk by ensuring no one has unnecessary permissions that could be exploited or misused.
Control Intent
Prevent unauthorized access to sensitive information and critical system functions by limiting user and process privileges to only what is necessary for legitimate business purposes, thereby reducing the attack surface and potential damage from compromised accounts.
Who This Control Applies To
- •All user accounts (employees, contractors, third parties) with access to CUI or systems processing CUI
- •All privileged accounts including system administrators, database administrators, and security administrators
- •Service accounts and automated processes that access CUI or perform security functions
- •Application-level accounts and roles within systems processing CUI
- •Domain accounts and local accounts on systems in scope
- •Development, testing, and production environments containing or processing CUI
Not Applicable When
- •The organization has no users with access to CUI or systems processing CUI
- •All systems are operated by a single individual who is also the owner (extremely rare and would require careful scoping justification)
- •Systems are completely isolated with no user accounts or access controls (not realistic for CMMC scope)
Key Objectives
- 1Users and processes are granted only the minimum privileges necessary to perform their assigned duties.
- 2Privileged accounts with elevated access rights are restricted to authorized personnel performing specific administrative functions.
- 3Security-relevant functions such as logging configuration, access control settings, and system administration are protected from unauthorized modification.
- 4Separation of duties is enforced where appropriate to prevent any single user from having excessive control over critical security functions.
Sample Self-Assessment Questions (Partial)
Do any of your users have administrator or elevated privileges on systems that store, process, or transmit CUI?
Are there users who have access to CUI but don't need it for their job responsibilities?
Implementation Approaches (High-Level)
Role-Based Access Control with Privileged Access Management
Implement role-based access control (RBAC) where permissions are assigned based on job functions, combined with privileged access management (PAM) solutions that enforce separation of standard and privileged accounts.
Principle of Least Privilege via Group Policy and Local Account Restrictions
Use Group Policy Objects (GPOs) in Windows environments or equivalent configuration management tools in other environments to enforce least privilege by removing local administrator rights and restricting user capabilities.
Application-Level Least Privilege with Database and System Role Separation
Enforce least privilege within applications, databases, and systems by creating granular roles and permissions that align with specific job functions and limiting privileged access to authorized personnel.
Privileged Access Workstations (PAWs) and Jump Servers
Implement dedicated workstations or jump servers for privileged administrative tasks, ensuring that privileged accounts are never used on standard user workstations or for internet browsing and email.
Just-In-Time (JIT) Privileged Access
Implement time-limited, on-demand privileged access where users request elevated permissions only when needed, and those permissions are automatically revoked after a defined period.
Least Privilege for Service Accounts and Automated Processes
Configure service accounts, application pools, scheduled tasks, and automated processes with the minimum permissions required to perform their specific functions, avoiding use of highly privileged accounts.
Evidence & Assessment Notes
Expected Evidence
Organizations should maintain documentation and evidence demonstrating compliance with this control. This may include policy documentation, configuration records, audit logs, access reviews, and other relevant artifacts that show how the control is implemented and maintained.
Plan of Action & Milestones (POA&M)
If users currently have local administrator rights without business justification, create a POA&M to remove these rights with a phased approach (e.g., pilot group, then broader rollout) If privileged accounts are used for day-to-day activities, create a POA&M to implement separate standard user accounts for administrators with a defined timeline If no access review process exists, create a POA&M to establish and document periodic access recertification with initial review completion date If service accounts have excessive permissions, create a POA&M to inventory service accounts and right-size permissions on a system-by-system basis If privileged account activities are not logged or monitored, create a POA&M to implement logging and establish a review process If least privilege is not enforced in cloud environments, create a POA&M to review and remediate cloud IAM policies and role assignments If application-level least privilege is not implemented, create a POA&M to define application roles and migrate users to least-privilege roles POA&Ms should include specific milestones (e.g., policy approval, technical implementation, user migration, validation testing) POA&Ms should identify resources required (e.g., PAM tools, training, consultant support) and any dependencies Interim compensating controls for POA&Ms might include enhanced monitoring, management review and approval, or restricted access to CUI until least privilege is fully implemented
Frequently Asked Questions
Does least privilege mean users can never have administrator rights on their workstations?
Not necessarily. Least privilege means users should only have the minimum permissions needed for their job duties. If a user's role genuinely requires local administrator rights (e.g., a developer needing to install and test software), this can be justified and documented. However, most standard business users (e.g., those doing email, document editing, web browsing) do not need administrator rights, and granting them violates least privilege. The key is documented business justification and regular review.
What is the difference between a privileged account and a standard user account?
A privileged account has elevated permissions that allow administrative functions such as installing software, changing security settings, creating user accounts, or accessing sensitive system configurations. A standard user account has only the permissions needed for routine business tasks like accessing applications and data relevant to the user's job. For least privilege compliance, administrators should have separate accounts: a standard account for daily work (email, documents) and a privileged account used only when performing administrative tasks.
How often do we need to review user access rights to comply with this control?
NIST SP 800-171 and CMMC do not specify an exact frequency, but industry best practice and assessor expectations typically require access reviews at least annually, with more frequent reviews (quarterly or semi-annually) for privileged accounts. The organization should define the review frequency in its access control policy based on risk, and then demonstrate consistent execution of reviews with documented results and remediation of findings.
Can we have exceptions to least privilege, and how should they be handled?
Yes, exceptions are allowed if there is a documented business or technical justification and appropriate compensating controls. For example, a legacy application might require users to have elevated permissions that would normally violate least privilege. In such cases, document the exception, the business justification, any compensating controls (e.g., enhanced monitoring, restricted access to CUI from that system), and obtain management approval. Exceptions should be reviewed periodically to determine if they can be eliminated.
Does this control apply to cloud environments and SaaS applications?
Yes, least privilege applies to all systems and applications that store, process, or transmit CUI, including cloud infrastructure (AWS, Azure, GCP) and SaaS applications (Microsoft 365, Salesforce, etc.). Users should be assigned cloud roles and SaaS application permissions based on their job duties, and privileged cloud accounts (e.g., global administrators, account owners) should be restricted and monitored. Many organizations fail assessments by overlooking least privilege in cloud environments.
What are common mistakes organizations make when implementing least privilege?
Common mistakes include: granting local administrator rights to all users for convenience; using privileged accounts for day-to-day activities like email; failing to conduct regular access reviews; not documenting role definitions and permission assignments; overlooking service accounts that run with excessive privileges; and implementing least privilege on-premises but not in cloud or SaaS environments. Another frequent issue is creating policies without technical enforcement, relying on users to follow procedures rather than using Group Policy, IAM policies, or other controls to enforce restrictions.
How ConformatIQ Helps With CMMC Readiness
ConformatIQ is an AI-assisted CMMC readiness platform designed to help organizations prepare for assessments more efficiently. The platform supports document generation such as SSPs and POA&Ms, guided readiness workflows, centralized evidence tracking, and interview preparation for assessments.
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Request Full GuidanceInformation sourced from NIST SP 800-171 Rev. 2. See full disclaimer.