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Description

The following analytic utilizes PowerShell Script Block Logging (EventCode=4104) to identify the use of PowerShell environment variables to identify the current logged user. Red Teams and adversaries may leverage this method to identify the logged user on a compromised endpoint for situational awareness and Active Directory Discovery.

  • Type: Hunting

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

  • Last Updated: 2022-03-22
  • Author: Mauricio Velazco, Splunk
  • ID: 77f41d9e-b8be-47e3-ab35-5776f5ec1d20

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1033 System Owner/User Discovery Discovery
Kill Chain Phase
  • Reconnaissance
NIST
CIS20
CVE 


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`powershell` EventCode=4104 (ScriptBlockText = "*$env:UserName*" OR ScriptBlockText = "*[System.Environment]::UserName*") 
| stats count min(_time) as firstTime max(_time) as lastTime by EventCode ScriptBlockText Computer user_id 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `user_discovery_with_env_vars_powershell_script_block_filter`

Macros

The SPL above uses the following Macros:

:information_source: user_discovery_with_env_vars_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
  • Path
  • Message
  • OpCode
  • ComputerName
  • User
  • EventCode

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

RBA

Risk Score Impact Confidence Message
15.0 30 50 System user discovery on $dest$

:information_source: 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

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: 2