Detection: Windows PowerShell Disabled Kerberos Pre-Authentication Discovery Get-ADUser

Description

The following analytic utilizes PowerShell Script Block Logging (EventCode=4104) to identify the execution of the Get-ADUser commandlet with specific parameters. Get-ADUser is part of the Active Directory PowerShell module used to manage Windows Active Directory networks. As the name suggests, Get-ADUser is used to query for domain users. With the appropiate parameters, Get-ADUser allows adversaries to discover domain accounts with Kerberos Pre Authentication disabled.\ Red Teams and adversaries alike use may abuse Get-ADUSer to enumerate these accounts and attempt to crack their passwords offline.

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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://docs.splunk.com/Documentation/UBA/5.0.4.1/GetDataIn/AddPowerShell#Configure_module_logging_for_PowerShell.

Known False Positives

Administrators or power users may use search for accounts with Kerberos Pre Authentication disabled for legitimate purposes.

Associated Analytic Story

• Active Directory Kerberos Attacks

Risk Based Analytics (RBA)

References

• https://attack.mitre.org/techniques/T1558/004/

• https://m0chan.github.io/2019/07/31/How-To-Attack-Kerberos-101.html

• https://stealthbits.com/blog/cracking-active-directory-passwords-with-as-rep-roasting/

Version: 4