sc-3-security-function-isolation

name	SC-3_security-function-isolation
description	Isolate security functions from nonsecurity functions.
category	configuration
version	5.2.0
author	cyberstrike-official
tags	["nist","sp800-53","rev5","sc-3","sc"]
tech_stack	["aws","azure","gcp","linux","windows","network"]
cwe_ids	["CWE-311"]
chains_with	["AC-3","AC-6","AC-25","CM-2","CM-4","SA-4","SA-5","SA-8","SA-15","SA-17"]
prerequisites	[]
severity_boost	{"AC-3":"Chain with AC-3 for comprehensive security coverage","AC-6":"Chain with AC-6 for comprehensive security coverage","AC-25":"Chain with AC-25 for comprehensive security coverage"}

SC-3 Security Function Isolation

High-Level Description

Family: System and Communications Protection (SC) Framework: NIST SP 800-53 Rev 5

Security functions are isolated from nonsecurity functions by means of an isolation boundary implemented within a system via partitions and domains. The isolation boundary controls access to and protects the integrity of the hardware, software, and firmware that perform system security functions. Systems implement code separation in many ways, such as through the provision of security kernels via processor rings or processor modes. For non-kernel code, security function isolation is often achieved through file system protections that protect the code on disk and address space protections that protect executing code. Systems can restrict access to security functions using access control mechanisms and by implementing least privilege capabilities. While the ideal is for all code within the defined security function isolation boundary to only contain security-relevant code, it is sometimes necessary to include nonsecurity functions as an exception. The isolation of security functions from nonsecurity functions can be achieved by applying the systems security engineering design principles in SA-8 , including SA-8(1), SA-8(3), SA-8(4), SA-8(10), SA-8(12), SA-8(13), SA-8(14) , and SA-8(18).

What to Check

• Verify SC-3 Security Function Isolation is documented in SSP
• Confirm control is operating effectively
• Review evidence of continuous monitoring for SC-3

How to Test

Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for SC-3 implementation details. Verify the organization has documented how this control is satisfied.

Step 2: Validate Implementation

# For cloud environments, use cloud-audit-mcp tools
# For on-premises, review system configurations directly

# Example: Check if account management policies exist
grep -r "account.management\|access.control" /etc/security/ 2>/dev/null

Step 3: Test Operating Effectiveness

Verify the control is actively functioning, not just documented. Check logs, configurations, and operational evidence.

Tools

Tool	Purpose