Windows Process Creation: DarkSide Ransomware Helper Command-Line Pattern

title: "Windows Process Creation: DarkSide Ransomware Helper Command-Line Pattern"
id: d8d727a0-a631-4a37-9e77-106747f2862f
status: test
description: This rule flags Windows process creation events where the command line contains a specific inline byte/char decoding expression and where the parent process command line matches a DllHost.exe invocation tied to a particular ProcessId. It aims to surface DarkSide ransomware helper behavior, where attackers use encoded command-line content and a scripting/host process to execute payload staging or execution steps. The detection relies on process creation telemetry including the Image, ParentCommandLine, and CommandLine fields.
references:
  - https://www.fireeye.com/blog/threat-research/2021/05/shining-a-light-on-darkside-ransomware-operations.html
  - https://app.any.run/tasks/8b9a571b-bcc1-4783-ba32-df4ba623b9c0/
  - https://www.joesandbox.com/analysis/411752/0/html#7048BB9A06B8F2DD9D24C77F389D7B2B58D2
  - https://github.com/SigmaHQ/sigma/blob/master/rules-emerging-threats/2021/Malware/DarkSide/proc_creation_win_malware_darkside_ransomware.yml
author: Florian Roth (Nextron Systems), Huntrule Team
date: 2021-05-14
tags:
  - attack.execution
  - attack.t1204
  - detection.emerging-threats
logsource:
  category: process_creation
  product: windows
detection:
  selection1:
    CommandLine|contains:
      - =[char][byte]('0x'+
      - " -work worker0 -path "
  selection2:
    ParentCommandLine|contains: DllHost.exe /Processid:{3E5FC7F9-9A51-4367-9063-A120244FBEC7}
    Image|contains: \AppData\Local\Temp\
  condition: 1 of selection*
falsepositives:
  - Unknown
  - UAC bypass method used by other malware
level: critical
license: DRL-1.1
related:
  - id: 965fff6c-1d7e-4e25-91fd-cdccd75f7d2c
    type: derived