PowerShell User Discovery and Export with Get-ADUser

Flags PowerShell Get-ADUser enumeration (filter *) followed by exporting results to a file.

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powershell-user-discovery-and-export-with-get-aduser-1114e048

title: PowerShell User Discovery and Export with Get-ADUser
id: 45fd0a9b-b046-4f53-a96b-e68fc4539e7e
related:
  - id: c2993223-6da8-4b1a-88ee-668b8bf315e9
    type: similar
  - id: 1114e048-b69c-4f41-bc20-657245ae6e3f
    type: derived
status: test
description: This rule identifies PowerShell execution of the Get-ADUser cmdlet with a broad filter ("-Filter *") and subsequent export of results to a file. Attackers use this to enumerate directory users for targeting, discovery, or later collection steps. It relies on Windows process creation telemetry capturing PowerShell command lines that include the Get-ADUser usage and file output via redirection or common output cmdlets.
references:
  - http://blog.talosintelligence.com/2022/09/lazarus-three-rats.html
  - https://www.microsoft.com/en-us/security/blog/2022/10/18/defenders-beware-a-case-for-post-ransomware-investigations/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_powershell_user_discovery_get_aduser.yml
author: Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2022-09-09
modified: 2022-11-17
tags:
  - attack.discovery
  - attack.t1033
logsource:
  category: process_creation
  product: windows
detection:
  selection_img:
    - Image|endswith:
        - \powershell.exe
        - \pwsh.exe
    - OriginalFileName:
        - PowerShell.EXE
        - pwsh.dll
  selection_cli:
    CommandLine|contains|all:
      - "Get-ADUser "
      - " -Filter \\*"
    CommandLine|contains:
      - " > "
      - " | Select "
      - Out-File
      - Set-Content
      - Add-Content
  condition: all of selection_*
falsepositives:
  - Legitimate admin scripts may use the same technique, it's better to exclude specific computers or users who execute these commands or scripts often
level: medium
license: DRL-1.1

What it detects

This rule identifies PowerShell execution of the Get-ADUser cmdlet with a broad filter ("-Filter *") and subsequent export of results to a file. Attackers use this to enumerate directory users for targeting, discovery, or later collection steps. It relies on Windows process creation telemetry capturing PowerShell command lines that include the Get-ADUser usage and file output via redirection or common output cmdlets.

Known false positives

Legitimate admin scripts may use the same technique, it's better to exclude specific computers or users who execute these commands or scripts often

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.