AD-SPN-04: Computer SPN unknown service class details should be investigated


ID	`AD-SPN-04`
Severity	Info
Suite	Active Directory (on-premises)
Product	Active Directory
Feature	Service principal names
Security area	Infrastructure hardening
Resource type	Computer
Reads from	On-premises Active Directory

What this checks and how to fix it

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.

Control Type

Operational

Security Recommendation

For each unknown SPN service class discovered:

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

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

Mito check. Author: soulemike. Open-source licences.

Open-source licences. CIS Benchmark material © Center for Internet Security, Inc.; CISA SCuBA baselines are public domain (CC0).