Detection: ServicePrincipalNames Discovery with PowerShell

Description

The following analytic identifies powershell.exe usage, using Script Block Logging EventCode 4104, related to querying the domain for Service Principle Names. typically, this is a precursor activity related to kerberoasting or the silver ticket attack.
What is a ServicePrincipleName?
A service principal name (SPN) is a unique identifier of a service instance. SPNs are used by Kerberos authentication to associate a service instance with a service logon account. This allows a client application to request that the service authenticate an account even if the client does not have the account name.
The following analytic identifies the use of KerberosRequestorSecurityToken class within the script block. Using .NET System.IdentityModel.Tokens.KerberosRequestorSecurityToken class in PowerShell is the equivelant of using setspn.exe.
During triage, review parallel processes for further suspicious activity.

Annotations

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Implementation

To successfully implement this analytic, you will need to enable PowerShell Script Block Logging on some or all endpoints. Additional setup here https://help.splunk.com/en/security-offerings/splunk-user-behavior-analytics/get-data-in/5.4.1/add-other-data-to-splunk-uba/configure-powershell-logging-to-see-powershell-anomalies-in-splunk-uba.

Known False Positives

False positives should be limited, however filter as needed.

Associated Analytic Story

• Active Directory Discovery

• Active Directory Kerberos Attacks

• Malicious PowerShell

• Active Directory Privilege Escalation

Risk Based Analytics (RBA)

References

• https://docs.microsoft.com/en-us/windows/win32/ad/service-principal-names

• https://docs.microsoft.com/en-us/dotnet/api/system.identitymodel.tokens.kerberosrequestorsecuritytoken?view=netframework-4.8

• https://www.ired.team/offensive-security-experiments/active-directory-kerberos-abuse/t1208-kerberoasting

• https://strontic.github.io/xcyclopedia/library/setspn.exe-5C184D581524245DAD7A0A02B51FD2C2.html

• https://attack.mitre.org/techniques/T1558/003/

• https://social.technet.microsoft.com/wiki/contents/articles/717.service-principal-names-spn-setspn-syntax.aspx

• https://web.archive.org/web/20220212163642/https://www.harmj0y.net/blog/powershell/kerberoasting-without-mimikatz/

• https://blog.zsec.uk/paving-2-da-wholeset/

• https://msitpros.com/?p=3113

• https://adsecurity.org/?p=3466

• https://help.splunk.com/en/security-offerings/splunk-user-behavior-analytics/get-data-in/5.4.1/add-other-data-to-splunk-uba/configure-powershell-logging-to-see-powershell-anomalies-in-splunk-uba.

• https://blog.palantir.com/tampering-with-windows-event-tracing-background-offense-and-defense-4be7ac62ac63

• https://static1.squarespace.com/static/552092d5e4b0661088167e5c/t/59c1814829f18782e24f1fe2/1505853768977/Windows+PowerShell+Logging+Cheat+Sheet+ver+Sept+2017+v2.1.pdf

• https://www.crowdstrike.com/blog/investigating-powershell-command-and-script-logging/

Version: 2