AC.L2-3.1.5 · NIST SP 800-171 3.1.5

Least Privilege

Employ the principle of least privilege, including for specific security functions and privileged accounts.

3 points if not metMust be fully met, cannot POA&M4 assessment objectives

What an assessor scores, the objectives

AC.L2-3.1.5 is met only when every one of these 4 objectives, from NIST SP 800-171A, is satisfied. A single missed objective makes the whole requirement not met.

  • a.privileged accounts are identified
  • b.access to privileged accounts is authorized in accordance with the principle of least privilege
  • c.se curity functions are identified
  • d.access to security functions is authorized in accordance with the principle of least privilege

How a C3PAO checks it

NIST SP 800-171A defines three assessment methods. For AC.L2-3.1.5, an assessor uses these:

Examine

Access control policy; procedures addressing account management; system security plan; system design documentation; system configuration settings and associated documentation; list of active system accounts and the name of the individual associated with each account; list of conditions for group and role membership; notifications or records of recently transferred, separated, or terminated employees; list of recently disabled system accounts along with the name of the individual associated with each account; access authorization records; account management compliance reviews; system monitoring/audit records; procedures addressing least privilege; list of security functions (deployed in hardware, software, and firmware) and security-relevant information for which access is to be explicitly authorized; list of system -generated privileged accounts; list of system administration personnel; other relevant documents or records

Interview

Personnel with account management responsibilities; system or network administrators; personnel with information security responsibilities; personnel with responsibilities for defining least privileges necessary to accomplish specified tasks

Test

Organizational processes for managing system accounts; mechanisms for implementing account management; mechanisms implementing least privilege functions; mechanisms prohibiting privileged access to the system

What it means, in context

Organizations employ the principle of least privilege for specific duties and authorized accesses for users and processes. The principle of least privilege is applied with the goal of authorized privileges no higher than necessary to accomplish required organizational missions or business functions. Organizations consider the creation of additional processes, roles, and system accounts as necessary, to achieve least privilege. Organizations also apply least privilege to the development, implementation, and operation of organizational systems. Security functions include establishing system accounts, setting events to be logged, setting intrusion detection parameters, and configuring access authorizations (i.e., permissions, privileges). Privileged accounts, including super user accounts, are typically described as system administrator for various types of commercial off- the-shelf operating systems. Restricting privileged accounts to specific personnel or roles prevents day -to-day users from having access to privileged information or functions. Organizations may differentiate in the application of this requirement between allowed privileges for local accounts and for domain accounts provided organizations retain the ability to control system configurations for key security parameters and as otherwise necessary to sufficiently mitigate risk.

The principle of least privilege applies to all users and processes on all systems, but it is critical to systems containing or accessing CUI. Least privilege: • restricts user access to only the machines and information needed to fulfill job responsibilities; and • limits what system configuration settings users can change, only allowing individuals with a business need to change them. Example You create accounts for an organization that processes CUI. By default, everyone is assigned a basic user role , which prevents a user from modifying system configurations. Privileged access is only assigned to users and processes that require it to carry out job functions, such as IT staff, and is very selectively granted [b,d]. Potential Assessment Considerations • Are privileged accounts documented and is when they may be used defined [a]? • Are users assigned privileged accounts to perform their job functions only when it is necessary [b]? • Are necessary security functions identified (e.g., access control configuration, system configuration settings, or privileged account lists) that must be managed through the use of privileged accounts [c]? • Is access to privileged functions and security information restricted to authorized employees [d]?

What passing evidence looks like

A list of privileged accounts and security functions, and proof each user holds only what their job needs: role screenshots with no blanket admin rights.

Common ways contractors fail AC.L2-3.1.5

  • !Global Administrator for daily work is the classic finding. Admins need a separate everyday account.
  • !Security functions include the antivirus console, firewall config, and audit settings, not just user management. Objective [c] wants them identified.

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AC.L2-3.1.5 questions, answered

How many points is CMMC requirement AC.L2-3.1.5 worth?+

AC.L2-3.1.5 is worth 3 points in the CMMC Level 2 score under 32 CFR 170.24. If it is not met, you lose 3 from your total of 110.

Can AC.L2-3.1.5 be placed on a POA&M?+

No. AC.L2-3.1.5 must be fully met before you can file. It cannot be deferred to a POA&M, so it is a gate on your assessment.

What family does AC.L2-3.1.5 belong to?+

AC.L2-3.1.5 is in the Access Control (AC) family, one of the 14 families of NIST SP 800-171 that make up CMMC Level 2.

Key references
  • NIST SP 800-171 Rev. 2 3.1.5