# AC-4(12)_data-type-identifiers

> When transferring information between different security domains, use [organization-defined] to validate data essential for information flow decisions

- Skill: `cyberstrikeus/ac-4-12-data-type-identifiers` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/ac-4-12-data-type-identifiers`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/ac-4-12-data-type-identifiers/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/ac-4-12-data-type-identifiers

---


# AC-4(12) Data Type Identifiers

> **Enhancement of:** AC-4

## High-Level Description

**Family:** Access Control (AC)
**Framework:** NIST SP 800-53 Rev 5

Data type identifiers include filenames, file types, file signatures or tokens, and multiple internal file signatures or tokens. Systems only allow transfer of data that is compliant with data type format specifications. Identification and validation of data types is based on defined specifications associated with each allowed data format. The filename and number alone are not used for data type identification. Content is validated syntactically and semantically against its specification to ensure that it is the proper data type.

## What to Check

- [ ] Verify AC-4(12) Data Type Identifiers is documented in SSP
- [ ] Confirm control is operating effectively
- [ ] Review evidence of continuous monitoring for AC-4(12)
- [ ] Verify enhancement builds upon base control AC-4

## How to Test

### Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for AC-4(12) 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 IAM policies and access controls | `cloud_audit_iam_policies` |
| hackbrowser | Test web application access controls   | `hackbrowser`        |

## Remediation Guide

### Control Statement

When transferring information between different security domains, use [organization-defined] to validate data essential for information flow decisions.

### Implementation Guidance

Data type identifiers include filenames, file types, file signatures or tokens, and multiple internal file signatures or tokens. Systems only allow transfer of data that is compliant with data type format specifications. Identification and validation of data types is based on defined specifications associated with each allowed data format. The filename and number alone are not used for data type identification. Content is validated syntactically and semantically against its specification to ensure that it is the proper data type.

## Risk Assessment

| Finding                                        | Severity | Impact                    |
| ---------------------------------------------- | -------- | ------------------------- |
| AC-4(12) Data Type Identifiers not implemented | High     | Access Control            |
| AC-4(12) partially implemented                 | Medium   | Incomplete Access Control |

## CWE Categories

| CWE ID  | Title                   |
| ------- | ----------------------- |
| CWE-284 | Improper Access Control |

## References

- [NIST SP 800-53 Rev 5 - AC-4(12)](https://csrc.nist.gov/projects/cprt/catalog#/cprt/framework/version/SP_800_53_5_1_1/home?element=ac-4.12)
- [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