Potential PowerShell Obfuscation Using Character Join

Detects specific techniques often seen used inside of PowerShell scripts to obfscuate Alias creation

Detection logic

selection

ScriptBlockText|contains|all:
  - -Alias
  - " -Value (-join("

Condition

selection

Raw YAML

title: Potential PowerShell Obfuscation Using Character Join
id: e8314f79-564d-4f79-bc13-fbc0bf2660d8
related:
    - id: 96cd126d-f970-49c4-848a-da3a09f55c55
      type: derived
status: test
description: Detects specific techniques often seen used inside of PowerShell scripts to obfscuate Alias creation
references:
    - Internal Research
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-01-09
tags:
    - attack.execution
    - attack.stealth
    - attack.t1027
    - attack.t1059.001
logsource:
    product: windows
    category: ps_script
    definition: 'Requirements: Script Block Logging must be enabled'
detection:
    selection:
        # Example:
        #   Set-Alias -Name Y -Value (-join("Ne","w-O","bje","ct"))
        #   Set-Alias -Name X -Value (-join("Inv","oke","-","Exp","ression"))
        ScriptBlockText|contains|all:
            - '-Alias' # For both "New-Alias" and "Set-Alias"
            - ' -Value (-join('
    condition: selection
falsepositives:
    - Unknown
level: low