Invoke-Obfuscation STDIN+ Launcher

Hunt Hypothesis

Detects Obfuscated use of stdin to execute PowerShell

Detection Rule

Sigma (Original)

title: Invoke-Obfuscation STDIN+ Launcher
id: 6c96fc76-0eb1-11eb-adc1-0242ac120002
status: test
description: Detects Obfuscated use of stdin to execute PowerShell
references:
    - https://github.com/SigmaHQ/sigma/issues/1009  # (Task 25)
author: Jonathan Cheong, oscd.community
date: 2020-10-15
modified: 2024-04-15
tags:
    - attack.stealth
    - attack.t1027
    - attack.execution
    - attack.t1059.001
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        # Example 1: c:\windows\sYstEm32\CmD.eXE /C"echO\Invoke-Expression (New-Object Net.WebClient).DownloadString | POwersHELl -NoEXiT -"
        # Example 2: c:\WiNDOws\sysTEm32\cmd.EXe /C " ECHo Invoke-Expression (New-Object Net.WebClient).DownloadString | POwersHELl -nol ${EXEcUtIONCONTeXT}.INvOkEComMANd.InvOKEScRIPt( $InpUt )"
        CommandLine|re: 'cmd.{0,5}(?:/c|/r).+powershell.+(?:\$\{?input\}?|noexit).+\"'
    condition: selection
falsepositives:
    - Unknown
level: high

KQL (Azure Sentinel)

imProcessCreate
| where TargetProcessCommandLine matches regex "cmd.{0,5}(?:/c|/r).+powershell.+(?:\\$\\{?input\\}?|noexit).+\\\""

Required Data Sources

False Positive Guidance

• Unknown

MITRE ATT&CK Context

• Tactic: Execution
• Technique: T1027 — T1027
• Technique: T1059.001 — PowerShell

References

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