# User SPN non-FQDN hosts should be investigated

User SPN non-FQDN hosts should be investigated. A Maester check for Active Directory, Service principal names.

Source: https://maester.dev/docs/tests/AD-SPN-11

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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 · Service principal names · <a href="/docs/tests">All checks</a></p>

```powershell title="Run this check"
Invoke-Maester -TestId AD-SPN-11
```

## Overview

User account SPNs with non-FQDN hosts can cause:

- **Authentication failures**: Kerberos may fail to resolve short names
- **Cross-domain issues**: Non-FQDNs don't work across domain trusts
- **Service disruptions**: Applications may fail to authenticate
- **Configuration drift**: Indicates inconsistent SPN management

Since user accounts with SPNs are already high-value targets, ensuring proper FQDN configuration is essential.

#### Control Type

**Operational**

#### Security Recommendation

Review and fix non-FQDN user SPNs:
- Update SPNs to use fully qualified domain names
- Establish SPN registration standards
- Use FQDNs consistently for all service principal names
- Consider this as part of a migration to gMSAs

#### How the Test Works

This test parses all user SPNs and checks if the host portion contains a dot (indicating FQDN format). SPNs without dots in the host portion are flagged as non-FQDN.

#### Related Tests

- `Test-MtAdComputerSpnNonFqdnHosts` - Checks computer SPNs for non-FQDN hosts
- `Test-MtAdUserSpnTotalCount` - Overall user SPN analysis

## Details

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

| Field | Value |
| --- | --- |
| Test ID | AD-SPN-11 |
| Severity | Info |
| Suite | Active Directory |
| Product | Active Directory |
| Feature | Service principal names |
| Area | Authentication |
| Resource type | User |
| MITRE ATT&CK | None |
| PowerShell test | [Test-MtAdUserSpnNonFqdnHosts](https://github.com/maester365/maester/blob/main/tests/ad/spn/Test.AD-SPN-11.ps1) |
| Services | ActiveDirectory |
| Permissions | ActiveDirectory:Ldap:user:ReadProperty |

</details>

## Source

- Test: [`tests/ad/spn/Test.AD-SPN-11.ps1`](https://github.com/maester365/maester/blob/main/tests/ad/spn/Test.AD-SPN-11.ps1)
- Documentation: [`tests/ad/spn/Test.AD-SPN-11.md`](https://github.com/maester365/maester/blob/main/tests/ad/spn/Test.AD-SPN-11.md)