title: Base64 Encoded Reflective Assembly Load
id: 62b7ccc9-23b4-471e-aa15-6da3663c4d59
status: test
description: Detects base64 encoded .NET reflective loading of Assembly
author: "Christian Burkard, pH-T"
related:
  - id: 9c0295ce-d60d-40bd-bd74-84673b7592b1
    type: similar
date: 2022/03/01
modified: 2022/05/20
tags:
    - attack.execution
    - attack.t1059.001
    - attack.defense_evasion
    - attack.t1027
references:
    - https://github.com/Neo23x0/Raccine/blob/main/yara/mal_revil.yar
    - https://thedfirreport.com/2022/05/09/seo-poisoning-a-gootloader-story/
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    CommandLine|contains:
      # [Reflection.Assembly]::Load(
      - 'WwBSAGUAZgBsAGUAYwB0AGkAbwBuAC4AQQBzAHMAZQBtAGIAbAB5AF0AOgA6AEwAbwBhAGQAKA'
      - 'sAUgBlAGYAbABlAGMAdABpAG8AbgAuAEEAcwBzAGUAbQBiAGwAeQBdADoAOgBMAG8AYQBkACgA'
      - 'bAFIAZQBmAGwAZQBjAHQAaQBvAG4ALgBBAHMAcwBlAG0AYgBsAHkAXQA6ADoATABvAGEAZAAoA'
      # [reflection.assembly]::("Load")
      - 'AFsAcgBlAGYAbABlAGMAdABpAG8AbgAuAGEAcwBzAGUAbQBiAGwAeQBdADoAOgAoACIATABvAGEAZAAiAC'
      - 'BbAHIAZQBmAGwAZQBjAHQAaQBvAG4ALgBhAHMAcwBlAG0AYgBsAHkAXQA6ADoAKAAiAEwAbwBhAGQAIgAp'
      - 'AWwByAGUAZgBsAGUAYwB0AGkAbwBuAC4AYQBzAHMAZQBtAGIAbAB5AF0AOgA6ACgAIgBMAG8AYQBkACIAK'
      # [Reflection.Assembly]::("Load")
      - 'WwBSAGUAZgBsAGUAYwB0AGkAbwBuAC4AQQBzAHMAZQBtAGIAbAB5AF0AOgA6ACgAIgBMAG8AYQBkACIAKQ'
      - 'sAUgBlAGYAbABlAGMAdABpAG8AbgAuAEEAcwBzAGUAbQBiAGwAeQBdADoAOgAoACIATABvAGEAZAAiACkA'
      - 'bAFIAZQBmAGwAZQBjAHQAaQBvAG4ALgBBAHMAcwBlAG0AYgBsAHkAXQA6ADoAKAAiAEwAbwBhAGQAIgApA'
      # [reflection.assembly]::Load(
      - 'WwByAGUAZgBsAGUAYwB0AGkAbwBuAC4AYQBzAHMAZQBtAGIAbAB5AF0AOgA6AEwAbwBhAGQAKA'
      - 'sAcgBlAGYAbABlAGMAdABpAG8AbgAuAGEAcwBzAGUAbQBiAGwAeQBdADoAOgBMAG8AYQBkACgA'
      - 'bAHIAZQBmAGwAZQBjAHQAaQBvAG4ALgBhAHMAcwBlAG0AYgBsAHkAXQA6ADoATABvAGEAZAAoA'
  condition: selection
fields:
  - CommandLine
falsepositives:
  - Unlikely
level: high