# Read-only domain controller count should be retrievable

Read-Only Domain Controllers (RODCs) are a critical security feature introduced in Windows Server 2008 designed specifically for deployment in locations…

Source: https://maester.dev/docs/tests/AD-DCD-03

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<div class="test-byline"><div class="test-byline-avatars"><a class="test-byline-avatar test-byline-avatar--author" href="/contributors/soulemike" title="Michael Soule · Original author"><img src="https://github.com/soulemike.png" alt="Michael Soule" width="28" height="28" loading="lazy" decoding="async" /></a></div><div class="test-byline-meta"><span class="test-byline-text">Contributed by <a href="/contributors/soulemike">Michael Soule</a></span><a class="test-byline-link" href="/contributors">All contributors →</a></div></div>

<p class="test-part">Part of <a href="/docs/tests/ad">Active Directory</a> · Active Directory · Domain controllers · <a href="/docs/tests">All checks</a></p>

```powershell title="Run this check"
Invoke-Maester -TestId AD-DCD-03
```

## Overview

Read-Only Domain Controllers (RODCs) are a critical security feature introduced in Windows Server 2008 designed specifically for deployment in locations where physical security cannot be guaranteed, such as branch offices. RODCs provide several security benefits:

- **Reduced attack surface**: RODCs maintain a read-only copy of the Active Directory database, preventing directory modifications from compromised locations
- **Credential caching control**: Administrators can configure which credentials (if any) are cached on the RODC, limiting exposure if the server is compromised
- **Read-only DNS**: RODCs can host read-only DNS zones, reducing DNS poisoning risks
- **Filtered attribute set**: Sensitive attributes can be prevented from replicating to RODCs

Understanding your RODC deployment helps ensure:
- Appropriate placement in less secure locations
- Proper credential caching policies
- Compliance with security standards for branch office infrastructure

#### Control Type

**Operational**

#### Security Recommendation

1. **Deploy RODCs in branch offices**: Use RODCs instead of writable DCs in locations with limited physical security
2. **Configure credential caching**: Limit cached credentials to only those needed for local operations
3. **Monitor RODC replication**: Regularly audit what data is being replicated to RODCs
4. **Plan for RODC compromise**: Have procedures in place for quickly resetting passwords if an RODC is compromised
5. **Review RODC placement**: Ensure all RODCs are justified and necessary

#### How the Test Works

This test retrieves all domain controllers and identifies which are configured as Read-Only Domain Controllers. The test reports:

- Total number of domain controllers
- Number of writable domain controllers
- Number of read-only domain controllers (RODCs)
- Names and sites of RODCs (if any exist)

#### Related Tests

- `Test-MtAdDcNonGlobalCatalogCount` - Checks Global Catalog configuration
- `Test-MtAdDcSiteCoverageCount` - Analyzes DC distribution across sites
- `Test-MtAdSiteWithoutDcCount` - Identifies sites without DC coverage

## Details

<details>
<summary>Every attribute of this check</summary>

| Field | Value |
| --- | --- |
| Test ID | AD-DCD-03 |
| Severity | Info |
| Suite | Active Directory |
| Product | Active Directory |
| Feature | Domain controllers |
| Area | Infrastructure hardening |
| Resource type | DomainController |
| MITRE ATT&CK | None |
| PowerShell test | [Test-MtAdDcReadOnlyCount](https://github.com/maester365/maester/blob/main/tests/ad/domain-controller/Test.AD-DCD-03.ps1) |
| Services | ActiveDirectory |
| Permissions | ActiveDirectory:Ldap:nTDSDSA:ReadProperty |

</details>

## Source

- Test: [`tests/ad/domain-controller/Test.AD-DCD-03.ps1`](https://github.com/maester365/maester/blob/main/tests/ad/domain-controller/Test.AD-DCD-03.ps1)
- Documentation: [`tests/ad/domain-controller/Test.AD-DCD-03.md`](https://github.com/maester365/maester/blob/main/tests/ad/domain-controller/Test.AD-DCD-03.md)