# User SPN service class usage should be investigated

User SPN service class usage should be investigated. A Maester check for Active Directory, Service principal names.

Source: https://maester.dev/docs/tests/AD-SPN-08

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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-08
```

## Overview

A detailed breakdown of SPN service classes on user accounts enables:

- **Risk prioritization**: Identify high-value targets like database services
- **Service inventory**: Understand what services run under user credentials
- **Compliance assessment**: Ensure services meet security standards
- **Migration planning**: Prioritize which services to move to gMSAs first

Database and application services on user accounts pose the highest Kerberoasting risk.

#### Control Type

**Operational**

#### Security Recommendation

Based on service class usage:
- Prioritize migrating database services (MSSQLSvc, oracle) to gMSAs
- Audit HTTP/HTTPS services running under user accounts
- Investigate custom or unknown service classes
- Document legitimate service accounts and their purposes

#### How the Test Works

This test analyzes all user SPNs, groups them by service class, and provides a count and percentage for each service class, helping you understand your user service account landscape.

#### Related Tests

- `Test-MtAdUserSpnServiceClassCount` - Counts distinct service classes
- `Test-MtAdUserSpnUnknownCount` - Identifies unrecognized service classes
- `Test-MtAdComputerSpnServiceClassUsage` - Computer account service class usage

## Details

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

| Field | Value |
| --- | --- |
| Test ID | AD-SPN-08 |
| Severity | Info |
| Suite | Active Directory |
| Product | Active Directory |
| Feature | Service principal names |
| Area | Authentication |
| Resource type | User |
| MITRE ATT&CK | T1558.003 Kerberoasting |
| PowerShell test | [Test-MtAdUserSpnServiceClassUsage](https://github.com/maester365/maester/blob/main/tests/ad/spn/Test.AD-SPN-08.ps1) |
| Services | ActiveDirectory |
| Permissions | ActiveDirectory:Ldap:user:ReadProperty |

</details>

## Source

- Test: [`tests/ad/spn/Test.AD-SPN-08.ps1`](https://github.com/maester365/maester/blob/main/tests/ad/spn/Test.AD-SPN-08.ps1)
- Documentation: [`tests/ad/spn/Test.AD-SPN-08.md`](https://github.com/maester365/maester/blob/main/tests/ad/spn/Test.AD-SPN-08.md)