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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.

  • Type: TTP

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

  • Last Updated: 2022-05-03
  • Author: Mauricio Velazco, Splunk
  • ID: 114c6bfe-9406-11ec-bcce-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1558 Steal or Forge Kerberos Tickets Credential Access
T1558.004 AS-REP Roasting Credential Access
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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 `powershell` EventCode=4104 (ScriptBlockText = "*Get-ADUser*" AND ScriptBlockText="*4194304*") 
| stats count min(_time)  as firstTime max(_time) as lastTime by Opcode Computer UserID EventCode ScriptBlockText 
| `security_content_ctime(firstTime)` 
| `disabled_kerberos_pre_authentication_discovery_with_get_aduser_filter`

Macros

The SPL above uses the following Macros:

:information_source: disabled_kerberos_pre-authentication_discovery_with_get-aduser_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • ScriptBlockText
  • Opcode
  • Computer
  • UserID
  • EventCode

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

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

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
54.0 60 90 Disabled Kerberos Pre-Authentication Discovery With Get-ADUser from $dest$

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

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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