Overview

Security Requirements for 03.04.08 Application Execution Policy

The process used to identify software programs that are not authorized to execute on systems is commonly referred to as blacklisting. The process used to identify software programs that are authorized to execute on systems is commonly referred to as whitelisting. Whitelisting is the stronger of the two policies for restricting software program execution. In addition to whitelisting, organizations consider verifying the integrity of whitelisted software programs using, for example, cryptographic checksums, digital signatures, or hash functions. Verification of whitelisted software can occur either prior to execution or at system startup.[SP 800-167] provides guidance on application whitelisting.

Assessment GuidanceExamine 0/13

How an assessor determines this requirement is met. Source: CMMC Assessment Guide – Level 2, Version 2.13 (NIST SP 800-171 Rev. 2).

Discussion

Organizations should determine their blacklisting or whitelisting policy and configure the system to manage software that is allowed to run. Blacklisting or deny-by-exception allows all software to run except if on an unauthorized software list such as what is maintained in antivirus solutions. Whitelisting or permit-by-exception does not allow any software to run except if on an authorized software list. The stronger policy of the two is whitelisting.

This requirement, CM.L2-3.4.8, requires the implementation of allow-lists and deny-lists for application software. It leverages CM.L2-3.4.1, which requires the organization to establish and maintain software inventories. This requirement, CM.L2-3.4.8, also extends CM.L2-3.4.9, which only requires control and monitoring of any user installed software.

Examples

  1. Example 1

    To improve your company’s protection from malware, you have decided to allow only designated programs to run. With additional research you identify a capability within the latest operating system that can control executables, scripts, libraries, or application installers run in your environment [c]. To ensure success you begin by authorizing digitally signed executables. Once they are deployed, you then plan to evaluate and deploy whitelisting for software libraries and scripts [c].

Assessment Methods

Examine
The process of reviewing, inspecting, observing, studying, or analyzing assessment objects (e.g., policies, procedures, plans, system designs, mechanisms) to facilitate understanding, achieve clarification, or obtain evidence.Example: An assessor reads the access control policy and inspects system configuration settings to confirm they match.

Not all of the evidence listed is required to meet this requirement — check the items your organization has collected.

Interview
The process of holding discussions with individuals or groups within an organization to facilitate understanding, achieve clarification, or identify the location of evidence.Example: An assessor asks a system administrator to describe how user accounts are approved, reviewed, and disabled.
  • Personnel with responsibilities for identifying software authorized or not authorized to execute on the system
  • Personnel with information security responsibilities
  • System or network administrators
Test
The process of exercising assessment objects (e.g., activities, mechanisms) under specified conditions to compare actual behavior with expected behavior.Example: An assessor attempts to sign in with a disabled account to confirm that access is denied.
  • Organizational process for identifying, reviewing, and updating programs authorized or not authorized to execute on the system
  • Process for implementing blacklisting or whitelisting
  • Mechanisms supporting or implementing blacklisting or whitelisting

Potential Assessment Considerations

  • Is the information system configured to only allow authorized software to run [a, b, c]?
  • Is the system configured to disallow running unauthorized software [a, b, c]?
  • Is there a defined list of software programs authorized to execute on the system [b]?
  • Is the authorization policy a deny-all, permit by exception for software allowed to execute on the system [a, b, c]?
  • Are automated mechanisms used to prevent program execution in accordance with defined lists (e.g., whitelisting) [a, b, c]?

Key References

NIST SP 800-171 Rev. 2 3.4.8

Evidence

  1. 03.04.08.a

    A policy specifying whether whitelisting or blacklisting is to be implemented is specified

  1. 03.04.08.b

    The software allowed to execute under whitelisting or denied use under blacklisting is specified

  1. 03.04.08.c

    Whitelisting to allow the execution of authorized software or blacklisting to prevent the use of unauthorized software is implemented as specified