# SA-9_external-system-services

> Require that providers of external system services comply with organizational security and privacy requirements and employ the following controls: ...

- Skill: `cyberstrikeus/sa-9-external-system-services` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/sa-9-external-system-services`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/sa-9-external-system-services/raw
- Safety review: PASS (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Security
- Author: cyberstrikeus (https://skillmd.com/u/cyberstrikeus)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/cyberstrikeus/sa-9-external-system-services

---


# SA-9 External System Services

## High-Level Description

**Family:** System and Services Acquisition (SA)
**Framework:** NIST SP 800-53 Rev 5

External system services are provided by an external provider, and the organization has no direct control over the implementation of the required controls or the assessment of control effectiveness. Organizations establish relationships with external service providers in a variety of ways, including through business partnerships, contracts, interagency agreements, lines of business arrangements, licensing agreements, joint ventures, and supply chain exchanges. The responsibility for managing risks from the use of external system services remains with authorizing officials. For services external to organizations, a chain of trust requires that organizations establish and retain a certain level of confidence that each provider in the consumer-provider relationship provides adequate protection for the services rendered. The extent and nature of this chain of trust vary based on relationships between organizations and the external providers. Organizations document the basis for the trust relationships so that the relationships can be monitored. External system services documentation includes government, service providers, end user security roles and responsibilities, and service-level agreements. Service-level agreements define the expectations of performance for implemented controls, describe measurable outcomes, and identify remedies and response requirements for identified instances of noncompliance.

## What to Check

- [ ] Verify SA-9 External System Services is documented in SSP
- [ ] Validate all 3 control requirements are implemented
- [ ] Confirm control is operating effectively
- [ ] Review evidence of continuous monitoring for SA-9

## How to Test

### Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for SA-9 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                           | Usage |
| ------------- | --------------------------------- | ----- |
| Manual Review | Documentation and interview-based | N/A   |

## Remediation Guide

### Control Statement

Require that providers of external system services comply with organizational security and privacy requirements and employ the following controls: [organization-defined];
Define and document organizational oversight and user roles and responsibilities with regard to external system services; and
Employ the following processes, methods, and techniques to monitor control compliance by external service providers on an ongoing basis: [organization-defined].

### Implementation Guidance

External system services are provided by an external provider, and the organization has no direct control over the implementation of the required controls or the assessment of control effectiveness. Organizations establish relationships with external service providers in a variety of ways, including through business partnerships, contracts, interagency agreements, lines of business arrangements, licensing agreements, joint ventures, and supply chain exchanges. The responsibility for managing risks from the use of external system services remains with authorizing officials. For services external to organizations, a chain of trust requires that organizations establish and retain a certain level of confidence that each provider in the consumer-provider relationship provides adequate protection for the services rendered. The extent and nature of this chain of trust vary based on relationships between organizations and the external providers. Organizations document the basis for the trust relationships so that the relationships can be monitored. External system services documentation includes government, service providers, end user security roles and responsibilities, and service-level agreements. Service-level agreements define the expectations of performance for implemented controls, describe measurable outcomes, and identify remedies and response requirements for identified instances of noncompliance.

## Risk Assessment

| Finding                                       | Severity | Impact                                     |
| --------------------------------------------- | -------- | ------------------------------------------ |
| SA-9 External System Services not implemented | Medium   | System and Services Acquisition            |
| SA-9 partially implemented                    | Low      | Incomplete System and Services Acquisition |

## CWE Categories

| CWE ID | Title         |
| ------ | ------------- |
| CWE-16 | Configuration |

## References

- [NIST SP 800-53 Rev 5 - SA-9](https://csrc.nist.gov/projects/cprt/catalog#/cprt/framework/version/SP_800_53_5_1_1/home?element=sa-9)
- [NIST SP 800-53A Rev 5 (Assessment Procedures)](https://csrc.nist.gov/pubs/sp/800/53/a/r5/final)
- [NIST SP 800-53 Rev 5 Full Catalog](https://csrc.nist.gov/pubs/sp/800/53/r5/upd1/final)

## Checklist

- [ ] Control documented in SSP
- [ ] Implementation evidence collected
- [ ] Operating effectiveness validated
- [ ] Continuous monitoring in place
- [ ] Related controls (AC-20, CA-3, CP-2, IR-4, IR-7) reviewed