GetLocalUser with PowerShell Script Block

Try in Splunk Security Cloud

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.

• Type: Hunting

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

• Last Updated: 2024-05-13
• Author: Mauricio Velazco, Splunk
• ID: 2e891cbe-0426-11ec-9c9c-acde48001122

Annotations

ATT&CK

ATT&CK

ID	Technique	Tactic
T1087	Account Discovery	Discovery

T1087.001

Local Account

Discovery

T1059.001

PowerShell

Execution

Kill Chain Phase

• Exploitation
• Installation

NIST

• DE.AE

CIS20

• CIS 10

CVE

Search

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

Macros

The SPL above uses the following Macros:

• powershell
• security_content_ctime

getlocaluser_with_powershell_script_block_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
• EventCode
• ScriptBlockText
• Computer
• UserID

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 this PowerShell commandlet for troubleshooting.

Associated Analytic Story

• Active Directory Discovery
• Malicious PowerShell

RBA

Risk Score	Impact	Confidence	Message
15.0	30	50	Local user discovery enumeration using PowerShell on $Computer$ by $user$

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

• https://attack.mitre.org/techniques/T1087/001/
• https://www.splunk.com/en_us/blog/security/hunting-for-malicious-powershell-using-script-block-logging.html

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

source | version: 3