Invoke-Obfuscation VAR++ LAUNCHER OBFUSCATION — Sigma Rule

Rule metadata and linked tags

Author: Timur Zinniatullin, oscd.community. Source status: test; severity: high. Source dates: 2020-10-13 / 2022-11-16.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 2a6949cf56af790826309606e032d04603c24fb53a8f2671dc39732ec23de50a

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: Invoke-Obfuscation VAR++ LAUNCHER OBFUSCATION
id: e9f55347-2928-4c06-88e5-1a7f8169942e
status: test
description: Detects Obfuscated Powershell via VAR++ LAUNCHER
references:
    - https://github.com/SigmaHQ/sigma/issues/1009 # (Task27)
author: Timur Zinniatullin, oscd.community
date: 2020-10-13
modified: 2022-11-16
tags:
    - attack.stealth
    - attack.t1027
    - attack.execution
    - attack.t1059.001
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        # CommandLine|re: '(?i)&&set.*(\{\d\}){2,}\\\"\s+?\-f.*&&.*cmd.*\/c' # FPs with |\/r
        # Example 1: CMD /C"sET KUR=Invoke-Expression (New-Object Net.WebClient).DownloadString&&Set MxI=C:\wINDowS\sYsWow64\winDOWspoWERSheLl\V1.0\PowerShelL.EXe ${ExEcut`IoN`cON`TExT}.\"invo`kEcoMm`A`ND\".( \"{2}{1}{0}\" -f 'pt','EscRi','INvOk' ).Invoke( ( .( \"{0}{1}\" -f'D','IR' ) ( \"{0}{1}\"-f'ENV:kU','R')).\"vAl`Ue\" )&& CMD /C%mXI%"
        # Example 2: c:\WiNDOWS\sYSTEm32\CmD.exE /C "sEt DeJLz=Invoke-Expression (New-Object Net.WebClient).DownloadString&&set yBKM=PoWERShelL -noeX ^^^&(\"{2}{0}{1}\"-f '-ItE','m','seT') ( 'V' + 'a'+ 'RiAblE:z8J' +'U2' + 'l' ) ([TYpE]( \"{2}{3}{0}{1}\"-f 'e','NT','e','NViRONM' ) ) ; ^^^& ( ( [sTrIng]${VE`Rbo`SepReFER`Ence})[1,3] + 'X'-joIN'')( ( (.('gI') ('V' + 'a' + 'RIAbLe:z8j' + 'u2' +'l' ) ).vALUe::( \"{2}{5}{0}{1}{6}{4}{3}\" -f 'IRo','Nm','GETE','ABlE','I','nv','enTVAr').Invoke(( \"{0}{1}\"-f'd','ejLz' ),( \"{1}{2}{0}\"-f'cEss','P','RO') )) )&& c:\WiNDOWS\sYSTEm32\CmD.exE /C %ybkm%"
        CommandLine|contains|all:
            - '&&set'
            - 'cmd'
            - '/c'
            - '-f'
        CommandLine|contains:
            - '{0}'
            - '{1}'
            - '{2}'
            - '{3}'
            - '{4}'
            - '{5}'
    condition: selection
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://github.com/SigmaHQ/sigma/issues/1009