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Detection rules › Sigma

Computer Discovery And Export Via Get-ADComputer Cmdlet - PowerShell

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

Detects usage of the Get-ADComputer cmdlet to collect computer information and output it to a file

MITRE ATT&CK coverage

TacticTechniques
DiscoveryT1033 System Owner/User Discovery

Event coverage

ProviderEventTitle
PowerShellEvent ID 4104Creating Scriptblock text (MessageNumber of MessageTotal).

Rule body yaml

title: Computer Discovery And Export Via Get-ADComputer Cmdlet - PowerShell
id: db885529-903f-4c5d-9864-28fe199e6370
related:
    - id: 435e10e4-992a-4281-96f3-38b11106adde
      type: similar
status: test
description: Detects usage of the Get-ADComputer cmdlet to collect computer 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/
    - https://www.cisa.gov/uscert/sites/default/files/publications/aa22-320a_joint_csa_iranian_government-sponsored_apt_actors_compromise_federal%20network_deploy_crypto%20miner_credential_harvester.pdf
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-11-17
tags:
    - attack.discovery
    - attack.t1033
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection:
        ScriptBlockText|contains|all:
            - 'Get-ADComputer '
            - ' -Filter \*'
        ScriptBlockText|contains:
            - ' | Select '
            - 'Out-File'
            - 'Set-Content'
            - 'Add-Content'
    condition: 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

selection

Stage 1: selection

selection:
    ScriptBlockText|contains|all:
        - 'Get-ADComputer '
        - ' -Filter \*'
    ScriptBlockText|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
ScriptBlockTextmatch
  • -Filter \* corpus 2 (sigma 2)
  • | Select corpus 2 (sigma 2)
  • Add-Content corpus 3 (sigma 3)
  • Get-ADComputer corpus 2 (sigma 2)
  • Out-File corpus 3 (sigma 3)
  • Set-Content corpus 3 (sigma 3)