Suspicious Invoke-Obfuscation COMPRESS OBFUSCATION - PowerShell Module (via ps_module)

title: Suspicious Invoke-Obfuscation COMPRESS OBFUSCATION - PowerShell Module (via ps_module)
id: 4306f8d4-057f-5076-ae7b-72ebc3029f4a
status: stable
description: This rule detects Obfuscated Powershell via COMPRESS OBFUSCATION
references:
    - https://attack.mitre.org/techniques/T1059/001/
    - https://attack.mitre.org/techniques/T1027/
    - https://github.com/SigmaHQ/sigma/issues/1009
author: Huntrule Team
date: 2026-05-18
tags:
    - attack.stealth
    - attack.t1027
    - attack.execution
    - attack.t1059.001
logsource:
    product: windows
    category: ps_module
    definition: 0ad03ef1-f21b-4a79-8ce8-e6900c54b65b
detection:
    selection_4103:
        Payload|contains|all:
            - 'new-object'
            - 'text.encoding]::ascii'
        Payload|contains:
            - 'system.io.compression.deflatestream'
            - 'system.io.streamreader'
        Payload|endswith: 'readtoend'
    condition: selection_4103
falsepositives:
    - Unknown
level: medium