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SOC 247
ITSP.10.17198
ISO 42001soon
ISO 27001soon

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98 controls

03.04.06Least functionalityITSP.10.171Configuration management

Official Requirement

A. Configure the system to provide only mission-essential capabilities. B. Prohibit or restrict use of the following functions, ports, protocols, connections, and services: [Assignment: organization-defined functions, ports, protocols, connections, and services]. C. Review the system [Assignment: organization-defined frequency] to identify unnecessary or nonsecure functions, ports, protocols, connections, and services. D. Disable or remove functions, ports, protocols, connections, and services that are unnecessary or nonsecure.

Source: Canadian Centre for Cyber Security ITSP.10.171 (2025), adapted from NIST SP 800-171 Rev. 3

In Plain English

Systems must only run the services, ports, and software they actually need to function. Everything else must be disabled or removed. Maintain a list of allowed and prohibited services, review it periodically, and actively disable anything unnecessary. This reduces the attack surface.

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The Trust Services Criteria referenced in this tool are published by the American Institute of Certified Public Accountants (AICPA) and incorporate principles from the Committee of Sponsoring Organizations of the Treadway Commission (COSO). Criteria descriptions are reproduced for reference purposes. All implementation guidance, evidence recommendations, and control language are original work by Truvo Cyber. ISO 27001 and ISO 42001 are standards published by the International Organization for Standardization (ISO). Framework and standard names are the property of their respective owners. This tool is not affiliated with, endorsed by, or certified by AICPA, COSO, or ISO.

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On-premises implementation and evidence

Least functionality and attack surface reduction

Implementation steps

  1. Disable unnecessary services, features, and roles on all servers and workstations during initial build based on the hardening baseline
  2. Configure host-based firewalls to block all inbound and outbound traffic except explicitly required ports
  3. Maintain a list of approved ports, protocols, and services for each system type; review and update quarterly
  4. Run periodic port scans to identify unauthorized listening services and remediate findings

Tools / systems

Evidence artifacts

Evidence frequency: Quarterly port scans; quarterly service list review