Detection: Get ADUser with PowerShell Script Block

Updated Date: 2024-10-17 ID: 21432e40-04f4-11ec-b7e6-acde48001122 Author: Teoderick Contreras, Mauricio Velazco, Splunk Type: Hunting Product: Splunk Enterprise Security

Description

The following analytic detects the execution of the Get-AdUser PowerShell cmdlet, which is used to enumerate all domain users. It leverages PowerShell Script Block Logging (EventCode=4104) to identify instances where this command is executed with a filter. This activity is significant as it may indicate an attempt by adversaries or Red Teams to gather information about domain users for situational awareness and Active Directory discovery. If confirmed malicious, this behavior could lead to further reconnaissance and potential exploitation of user accounts within the domain.

Search

1`powershell` EventCode=4104 ScriptBlockText = "*get-aduser*" ScriptBlockText = "*-filter*" 
2| stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer UserID 
3| rename Computer as dest, UserID as user
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `get_aduser_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

Name	Value
powershell	`(source=WinEventLog:Microsoft-Windows-PowerShell/Operational OR source="XmlWinEventLog:Microsoft-Windows-PowerShell/Operational")`
get_aduser_with_powershell_script_block_filter	`search *`

get_aduser_with_powershell_script_block_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1087.002	Domain Account	Discovery
T1087	Account Discovery	Discovery

KillChainPhase.EXPLOITAITON

NistCategory.DE_AE

Cis18Value.CIS_10

APT41

BRONZE BUTLER

Chimera

Dragonfly

FIN13

FIN6

Fox Kitten

INC Ransom

Ke3chang

LAPSUS$

MuddyWater

OilRig

Poseidon Group

RedCurl

Sandworm Team

Scattered Spider

ToddyCat

Turla

Volt Typhoon

Wizard Spider

menuPass

Aquatic Panda

FIN13

Default Configuration

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

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Risk Event	False

This configuration file applies to all detections of type hunting.

Implementation

The following Hunting analytic requires PowerShell operational logs to be imported. Modify the powershell macro as needed to match the sourcetype or add index. This analytic is specific to 4104, or PowerShell Script Block Logging.

Known False Positives

Administrators or power users may use this command for troubleshooting.

Associated Analytic Story

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
Powershell process having commandline "get-aduser" for user enumeration on $dest$	25	50	50

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

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-PowerShell/Operational`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-PowerShell/Operational`	`XmlWinEventLog`

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: 4