AD-SPN-04 - Computer SPN unknown service class details should be retrievable

Contributed by Michael Soule with Merill FernandoAll contributors →

Overview

Detailed information about unknown SPNs enables security teams to:

• Investigate effectively: Know exactly which computers have unknown SPNs
• Assess scope: Understand how widespread an unknown service is
• Track down owners: Identify the computers to contact administrators
• Document exceptions: Build a list of authorized custom SPNs

This granular visibility is essential for maintaining SPN hygiene and security.

Security Recommendation

For each unknown SPN service class discovered:

1. Identify the service owner or application team
2. Determine if the service is legitimate and necessary
3. Verify the SPN is registered on the correct account (not a user account for a computer service)
4. Document approved custom SPNs in your security baseline
5. Remove or correct unauthorized SPNs

How the Test Works

This test analyzes all computer SPNs, compares service classes against a known database, and provides a detailed breakdown of unknown service classes including which computers have them and how many instances exist.

Related Tests

• Test-MtAdComputerSpnUnknownCount - Counts unknown service classes
• Test-MtAdUserSpnUnknownDetails - Details of unknown user account SPNs
• Test-MtAdComputerSpnServiceClassUsage - All service class usage breakdown

Test Metadata

Field	Value
Test ID	AD-SPN-04
Severity	Info
Suite	Active Directory
Category	AD.SPN
PowerShell test	Test-MtAdComputerSpnUnknownDetails
Tags	AD, AD-SPN-04, AD.SPN

Source

• Pester test: tests/ad/spn/Test-MtAdComputerSpnUnknownDetails.Tests.ps1
• PowerShell source: powershell/public/ad/spn/Test-MtAdComputerSpnUnknownDetails.ps1