CM-7: Least Functionality
Control Family:
Threats Addressed:
Next Version:
- NIST Special Publication 800-53 Revision 5:
- CM-7: Least Functionality
Control Statement
The organization:
- Configures the information system to provide only essential capabilities; and
- Prohibits or restricts the use of the following functions, ports, protocols, and/or services: [Assignment: organization-defined prohibited or restricted functions, ports, protocols, and/or services].
Supplemental Guidance
Information systems can provide a wide variety of functions and services. Some of the functions and services, provided by default, may not be necessary to support essential organizational operations (e.g., key missions, functions). Additionally, it is sometimes convenient to provide multiple services from single information system components, but doing so increases risk over limiting the services provided by any one component. Where feasible, organizations limit component functionality to a single function per device (e.g., email servers or web servers, but not both). Organizations review functions and services provided by information systems or individual components of information systems, to determine which functions and services are candidates for elimination (e.g., Voice Over Internet Protocol, Instant Messaging, auto-execute, and file sharing). Organizations consider disabling unused or unnecessary physical and logical ports/protocols (e.g., Universal Serial Bus, File Transfer Protocol, and Hyper Text Transfer Protocol) on information systems to prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling. Organizations can utilize network scanning tools, intrusion detection and prevention systems, and end-point protections such as firewalls and host-based intrusion detection systems to identify and prevent the use of prohibited functions, ports, protocols, and services.
Control Enhancements
CM-7(1): Periodic Review
Baseline(s):
- Moderate
- High
The organization: Reviews the information system [Assignment: organization-defined frequency] to identify unnecessary and/or nonsecure functions, ports, protocols, and services; and Disables [Assignment: organization-defined functions, ports, protocols, and services within the information system deemed to be unnecessary and/or nonsecure].
CM-7(2): Prevent Program Execution
Baseline(s):
- Moderate
- High
The information system prevents program execution in accordance with [Selection (one or more): [Assignment: organization-defined policies regarding software program usage and restrictions]; rules authorizing the terms and conditions of software program usage].
CM-7(3): Registration Compliance
Baseline(s):
The organization ensures compliance with [Assignment: organization-defined registration requirements for functions, ports, protocols, and services].
CM-7(4): Unauthorized Software / Blacklisting
Baseline(s):
- Moderate
The organization: Identifies [Assignment: organization-defined software programs not authorized to execute on the information system]; Employs an allow-all, deny-by-exception policy to prohibit the execution of unauthorized software programs on the information system; and Reviews and updates the list of unauthorized software programs [Assignment: organization-defined frequency].
CM-7(5): Authorized Software / Whitelisting
Baseline(s):
- High
The organization: Identifies [Assignment: organization-defined software programs authorized to execute on the information system]; Employs a deny-all, permit-by-exception policy to allow the execution of authorized software programs on the information system; and Reviews and updates the list of authorized software programs [Assignment: organization-defined frequency].