# Computer SPN non-FQDN hosts should be investigated

SPNs should use fully qualified domain names (FQDNs) for the host portion to ensure proper Kerberos authentication across domain boundaries and to avoid…

Source: https://maester.dev/docs/tests/AD-SPN-05

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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-05
```

## Overview

SPNs should use fully qualified domain names (FQDNs) for the host portion to ensure proper Kerberos authentication across domain boundaries and to avoid ambiguity. Non-FQDN hosts can cause:

- **Authentication failures**: Kerberos may fail to find the correct service principal
- **DNS resolution issues**: Short names may not resolve correctly in all contexts
- **Cross-domain problems**: Non-FQDNs may not work across domain trusts
- **Configuration drift**: Indicates inconsistent SPN registration practices

#### Control Type

**Operational**

#### Security Recommendation

Review SPNs with non-FQDN hosts:
- Determine if the SPN is still needed
- Update SPNs to use FQDN format (serviceclass/host.fqdn:port)
- Establish standards for SPN registration in your organization
- Use FQDNs consistently for all service principal names

#### How the Test Works

This test parses all computer 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-MtAdUserSpnNonFqdnHosts` - Checks user account SPNs for non-FQDN hosts
- `Test-MtAdComputerSpnServiceClassCount` - Overall SPN analysis

## Details

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

| Field | Value |
| --- | --- |
| Test ID | AD-SPN-05 |
| Severity | Info |
| Suite | Active Directory |
| Product | Active Directory |
| Feature | Service principal names |
| Area | Infrastructure hardening |
| Resource type | Computer |
| MITRE ATT&CK | None |
| PowerShell test | [Test-MtAdComputerSpnNonFqdnHosts](https://github.com/maester365/maester/blob/main/tests/ad/spn/Test.AD-SPN-05.ps1) |
| Services | ActiveDirectory |
| Permissions | ActiveDirectory:Ldap:computer:ReadProperty |

</details>

## Source

- Test: [`tests/ad/spn/Test.AD-SPN-05.ps1`](https://github.com/maester365/maester/blob/main/tests/ad/spn/Test.AD-SPN-05.ps1)
- Documentation: [`tests/ad/spn/Test.AD-SPN-05.md`](https://github.com/maester365/maester/blob/main/tests/ad/spn/Test.AD-SPN-05.md)