Suspicious Encoded PowerShell Command Line — Sigma Rule

Rule metadata and linked tags

Author: Florian Roth (Nextron Systems), Markus Neis, Jonhnathan Ribeiro, Daniil Yugoslavskiy, Anton Kutepov, oscd.community. Source status: test; severity: high. Source dates: 2018-09-03 / 2023-04-06.

{
  "category": "process_creation",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: d09f16965f8a5d45ddbfc0cf62a393753aefe90854ea10cbde017f65d138322f

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Suspicious Encoded PowerShell Command Line
id: ca2092a1-c273-4878-9b4b-0d60115bf5ea
status: test
description: Detects suspicious powershell process starts with base64 encoded commands (e.g. Emotet)
references:
    - https://app.any.run/tasks/6217d77d-3189-4db2-a957-8ab239f3e01e
author: Florian Roth (Nextron Systems), Markus Neis, Jonhnathan Ribeiro, Daniil Yugoslavskiy, Anton Kutepov, oscd.community
date: 2018-09-03
modified: 2023-04-06
tags:
    - attack.execution
    - attack.t1059.001
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith:
              - '\powershell.exe'
              - '\pwsh.exe'
        - OriginalFileName:
              - 'PowerShell.EXE'
              - 'pwsh.dll'
    selection_cli_enc:
        CommandLine|contains: ' -e' # covers -en and -enc
    selection_cli_content:
        CommandLine|contains:
            - ' JAB'
            - ' SUVYI'
            - ' SQBFAFgA'
            - ' aQBlAHgA'
            - ' aWV4I'
            - ' IAA'
            - ' IAB'
            - ' UwB'
            - ' cwB'
    selection_standalone:
        CommandLine|contains:
            - '.exe -ENCOD '
            - ' BA^J e-' # Reversed
    filter_optional_remote_signed:
        CommandLine|contains: ' -ExecutionPolicy remotesigned '
    condition: selection_img and (all of selection_cli_* or selection_standalone) and not 1 of filter_optional_*
level: high

Original YAML and metadata in JSON

False positives

No reviewed association in this snapshot.

Source references

• https://app.any.run/tasks/6217d77d-3189-4db2-a957-8ab239f3e01e