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Detection rules › Sigma

User Discovery And Export Via Get-ADUser Cmdlet

Status
test
Severity
medium
Log source
product windows, category process_creation
Author
Nasreddine Bencherchali (Nextron Systems)
Source
github.com/SigmaHQ/sigma

Detects usage of the Get-ADUser cmdlet to collect user information and output it to a file

MITRE ATT&CK coverage

TacticTechniques
DiscoveryT1033 System Owner/User Discovery

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

title: User Discovery And Export Via Get-ADUser Cmdlet
id: 1114e048-b69c-4f41-bc20-657245ae6e3f
related:
    - id: c2993223-6da8-4b1a-88ee-668b8bf315e9
      type: similar
status: test
description: Detects usage of the Get-ADUser cmdlet to collect user information and output it to a file
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/
author: Nasreddine Bencherchali (Nextron Systems)
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

Stages and Predicates

Stage 0: condition

all of selection_*

Stage 1: selection_img

selection_img:
    - Image|endswith:
          - '\powershell.exe'
          - '\pwsh.exe'
    - OriginalFileName:
          - 'PowerShell.EXE'
          - 'pwsh.dll'

Stage 2: selection_cli

selection_cli:
    CommandLine|contains|all:
        - 'Get-ADUser '
        - ' -Filter \*'
    CommandLine|contains:
        - ' > '
        - ' | Select '
        - 'Out-File'
        - 'Set-Content'
        - 'Add-Content'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
CommandLinematch
  • -Filter \* corpus 2 (sigma 2)
  • > corpus 5 (sigma 5)
  • | Select corpus 2 (sigma 2)
  • Add-Content corpus 2 (sigma 2)
  • Get-ADUser
  • Out-File corpus 3 (sigma 3)
  • Set-Content corpus 2 (sigma 2)
Imageends_with
  • \powershell.exe corpus 182 (sigma 182)
  • \pwsh.exe corpus 168 (sigma 168)
OriginalFileNameeq
  • PowerShell.EXE corpus 120 (sigma 84, splunk 30, elastic 6)
  • pwsh.dll corpus 112 (sigma 79, splunk 30, elastic 3)