SI 19(8) Motivated Intruder

---
name: "SI-19(8)_motivated-intruder"
description: "Perform a motivated intruder test on the de-identified dataset to determine if the identified data remains or if the de-identified data can be re-iden"
category: "input-validation"
version: "5.2.0"
author: "cyberstrike-official"
tags:
  - nist
  - sp800-53
  - rev5
  - si-19-8
  - si
  - enhancement
tech_stack:
  - aws
  - azure
  - gcp
  - linux
  - windows
cwe_ids:
  - CWE-20
chains_with: []
prerequisites:
  - SI-19
severity_boost: {}
---

# SI-19(8) Motivated Intruder

> **Enhancement of:** SI-19

## High-Level Description

**Family:** System and Information Integrity (SI)
**Framework:** NIST SP 800-53 Rev 5

A motivated intruder test is a test in which an individual or group takes a data release and specified resources and attempts to re-identify one or more individuals in the de-identified dataset. Such tests specify the amount of inside knowledge, computational resources, financial resources, data, and skills that intruders possess to conduct the tests. A motivated intruder test can determine if the de-identification is insufficient. It can also be a useful diagnostic tool to assess if de-identification is likely to be sufficient. However, the test alone cannot prove that de-identification is sufficient.

## What to Check

- [ ] Verify SI-19(8) Motivated Intruder is documented in SSP
- [ ] Confirm control is operating effectively
- [ ] Review evidence of continuous monitoring for SI-19(8)
- [ ] Verify enhancement builds upon base control SI-19

## How to Test

### Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for SI-19(8) 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                          |
| --------------- | -------------------------- | ------------------------------ |
| cloud-audit-mcp | Check integrity monitoring | `cloud_audit_monitoring`       |
| AWS CLI         | Review GuardDuty/Inspector | `aws guardduty list-detectors` |

## Remediation Guide

### Control Statement

Perform a motivated intruder test on the de-identified dataset to determine if the identified data remains or if the de-identified data can be re-identified.

### Implementation Guidance

A motivated intruder test is a test in which an individual or group takes a data release and specified resources and attempts to re-identify one or more individuals in the de-identified dataset. Such tests specify the amount of inside knowledge, computational resources, financial resources, data, and skills that intruders possess to conduct the tests. A motivated intruder test can determine if the de-identification is insufficient. It can also be a useful diagnostic tool to assess if de-identification is likely to be sufficient. However, the test alone cannot prove that de-identification is sufficient.

## Risk Assessment

| Finding                                     | Severity | Impact                                      |
| ------------------------------------------- | -------- | ------------------------------------------- |
| SI-19(8) Motivated Intruder not implemented | High     | System and Information Integrity            |
| SI-19(8) partially implemented              | Medium   | Incomplete System and Information Integrity |

## CWE Categories

| CWE ID | Title                     |
| ------ | ------------------------- |
| CWE-20 | Improper Input Validation |

## References

- [NIST SP 800-53 Rev 5 - SI-19(8)](https://csrc.nist.gov/projects/cprt/catalog#/cprt/framework/version/SP_800_53_5_1_1/home?element=si-19.8)
- [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 (none) reviewed