Detection: GetLocalUser with PowerShell Script Block

Description

The following analytic detects the execution of the Get-LocalUser PowerShell commandlet using PowerShell Script Block Logging (EventCode=4104). This commandlet lists all local users on a system. The detection leverages script block text from PowerShell logs to identify this activity. Monitoring this behavior is significant as adversaries and Red Teams may use it to enumerate local users for situational awareness and Active Directory discovery. If confirmed malicious, this activity could lead to further reconnaissance, enabling attackers to identify potential targets for privilege escalation or lateral movement.

Search

1`powershell` EventCode=4104 (ScriptBlockText = "*Get-LocalUser*") 
2| stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer user_id 
3| `security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)` 
5| `getlocaluser_with_powershell_script_block_filter`

Data Source

Name	Platform	Sourcetype	Source
Powershell Script Block Logging 4104	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-PowerShell/Operational'

Macros Used

Annotations

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

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 this PowerShell commandlet for troubleshooting.

Associated Analytic Story

• Active Directory Discovery

• Malicious PowerShell

References

• https://attack.mitre.org/techniques/T1087/001/

• https://www.splunk.com/en_us/blog/security/hunting-for-malicious-powershell-using-script-block-logging.html

Detection Testing

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

Source: GitHub | Version: 5