GetWmiObject User Account with PowerShell Script Block

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Description

The following analytic utilizes PowerShell Script Block Logging (EventCode=4104) to identify the execution of the Get-WmiObject commandlet used with specific parameters. The Win32_UserAccount parameter is used to return a list of all local users. Red Teams and adversaries may leverage this commandlet to enumerate users for situational awareness and Active Directory Discovery.

• Type: Hunting

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

• Last Updated: 2022-05-02
• Author: Mauricio Velazco, Splunk
• ID: 640b0eda-0429-11ec-accd-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

• Reconnaissance

NIST

CIS20

CVE

Search

`powershell` EventCode=4104 (ScriptBlockText="*Get-WmiObject*" AND ScriptBlockText="*Win32_UserAccount*") 
| stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer UserID 
| `security_content_ctime(firstTime)` 
| `getwmiobject_user_account_with_powershell_script_block_filter`

Macros

The SPL above uses the following Macros:

• powershell
• security_content_ctime

getwmiobject_user_account_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 $UserID$

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

• https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1087.001/AD_discovery/windows-powershell.log

source | version: 2