# AU-9(1)_hardware-write-once-media

> Write audit trails to hardware-enforced, write-once media.

- Skill: `cyberstrikeus/au-9-1-hardware-write-once-media` (Agent Skill)
- Install (CLI): `npx skillmds@latest add cyberstrikeus/au-9-1-hardware-write-once-media`
- Raw SKILL.md: https://api.skillmd.com/api/skills/cyberstrikeus/au-9-1-hardware-write-once-media/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/au-9-1-hardware-write-once-media

---


# AU-9(1) Hardware Write-once Media

> **Enhancement of:** AU-9

## High-Level Description

**Family:** Audit and Accountability (AU)
**Framework:** NIST SP 800-53 Rev 5

Writing audit trails to hardware-enforced, write-once media applies to the initial generation of audit trails (i.e., the collection of audit records that represents the information to be used for detection, analysis, and reporting purposes) and to the backup of those audit trails. Writing audit trails to hardware-enforced, write-once media does not apply to the initial generation of audit records prior to being written to an audit trail. Write-once, read-many (WORM) media includes Compact Disc-Recordable (CD-R), Blu-Ray Disc Recordable (BD-R), and Digital Versatile Disc-Recordable (DVD-R). In contrast, the use of switchable write-protection media, such as tape cartridges, Universal Serial Bus (USB) drives, Compact Disc Re-Writeable (CD-RW), and Digital Versatile Disc-Read Write (DVD-RW) results in write-protected but not write-once media.

## What to Check

- [ ] Verify AU-9(1) Hardware Write-once Media is documented in SSP
- [ ] Confirm control is operating effectively
- [ ] Review evidence of continuous monitoring for AU-9(1)
- [ ] Verify enhancement builds upon base control AU-9

## How to Test

### Step 1: Review Documentation

Examine the System Security Plan (SSP) and related artifacts for AU-9(1) 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 logging configuration  | `cloud_audit_logging`            |
| AWS CLI         | Review CloudTrail/CloudWatch | `aws cloudtrail describe-trails` |

## Remediation Guide

### Control Statement

Write audit trails to hardware-enforced, write-once media.

### Implementation Guidance

Writing audit trails to hardware-enforced, write-once media applies to the initial generation of audit trails (i.e., the collection of audit records that represents the information to be used for detection, analysis, and reporting purposes) and to the backup of those audit trails. Writing audit trails to hardware-enforced, write-once media does not apply to the initial generation of audit records prior to being written to an audit trail. Write-once, read-many (WORM) media includes Compact Disc-Recordable (CD-R), Blu-Ray Disc Recordable (BD-R), and Digital Versatile Disc-Recordable (DVD-R). In contrast, the use of switchable write-protection media, such as tape cartridges, Universal Serial Bus (USB) drives, Compact Disc Re-Writeable (CD-RW), and Digital Versatile Disc-Read Write (DVD-RW) results in write-protected but not write-once media.

## Risk Assessment

| Finding                                           | Severity | Impact                              |
| ------------------------------------------------- | -------- | ----------------------------------- |
| AU-9(1) Hardware Write-once Media not implemented | Medium   | Audit and Accountability            |
| AU-9(1) partially implemented                     | Low      | Incomplete Audit and Accountability |

## CWE Categories

| CWE ID  | Title                |
| ------- | -------------------- |
| CWE-778 | Insufficient Logging |

## References

- [NIST SP 800-53 Rev 5 - AU-9(1)](https://csrc.nist.gov/projects/cprt/catalog#/cprt/framework/version/SP_800_53_5_1_1/home?element=au-9.1)
- [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 (AU-4, AU-5) reviewed