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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.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2021-10-14
  • Author: Michael Haag, Splunk
  • ID: 13243068-2d38-11ec-8908-acde48001122

Annotations

ATT&CK
ID Technique Tactic
T1558.003 Kerberoasting Credential Access
Kill Chain Phase
  • Exploitation
NIST
CIS20
CVE
1
2
3
4
5
`powershell` EventCode=4104 Message="*KerberosRequestorSecurityToken*" 
| stats count min(_time) as firstTime max(_time) as lastTime by Message OpCode ComputerName User EventCode 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `serviceprincipalnames_discovery_with_powershell_filter`

Macros

The SPL above uses the following Macros:

Note that serviceprincipalnames_discovery_with_powershell_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required field

  • _time
  • Processes.dest
  • Processes.user
  • Processes.parent_process_name
  • Processes.parent_process
  • Processes.original_file_name
  • Processes.process_name
  • Processes.process
  • Processes.process_id
  • Processes.parent_process_path
  • Processes.process_path
  • Processes.parent_process_id

How To Implement

To successfully implement this analytic, you will need to enable PowerShell Script Block Logging on some or all endpoints. Additional setup here https://docs.splunk.com/Documentation/UBA/5.0.4.1/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell.

Known False Positives

False positives should be limited, however filter as needed.

Associated Analytic story

RBA

Risk Score Impact Confidence Message
80.0 80 100 An instance of $parent_process_name$ spawning $process_name$ was identified on endpoint $dest$ by user $user$ attempting to identify service principle names.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

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