Detection: Windows Account Discovery for None Disable User Account

Updated Date: 2024-05-26 ID: eddbf5ba-b89e-47ca-995e-2d259804e55e Author: Teoderick Contreras, Splunk Type: Hunting Product: Splunk Enterprise Security

Description

The following analytic detects the execution of the PowerView PowerShell cmdlet Get-NetUser with the UACFilter parameter set to NOT_ACCOUNTDISABLE, indicating an attempt to enumerate Active Directory user accounts that are not disabled. This detection leverages PowerShell Script Block Logging (EventCode 4104) to identify the specific script block text. Monitoring this activity is significant as it may indicate reconnaissance efforts by an attacker to identify active user accounts for further exploitation. If confirmed malicious, this activity could lead to unauthorized access, privilege escalation, or lateral movement within the network.

Search

1`powershell` EventCode=4104  ScriptBlockText = "*Get-NetUser*" ScriptBlockText = "*NOT_ACCOUNTDISABLE*" ScriptBlockText = "*-UACFilter*" 
2| rename Computer as dest, UserID as user 
3| stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText dest user 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `windows_account_discovery_for_none_disable_user_account_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Powershell Script Block Logging 4104	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-PowerShell/Operational'`	N/A

Macros Used

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

windows_account_discovery_for_none_disable_user_account_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	Account Discovery	Discovery
T1087.001	Local Account	Discovery

KillChainPhase.EXPLOITAITON

NistCategory.DE_AE

Cis18Value.CIS_10

FIN13

APT1

APT3

APT32

APT41

Chimera

Fox Kitten

Ke3chang

Moses Staff

OilRig

Poseidon Group

Threat Group-3390

Turla

admin@338

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

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 may leverage PowerView for legitimate purposes, filter as needed.

Associated Analytic Story

CISA AA23-347A

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
Windows Account Discovery for None Disable User Account using PowerView's Get-NetUser on $dest$.	15	30	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: 3