Invoke-Obfuscation COMPRESS OBFUSCATION - PowerShell

Title: Invoke-Obfuscation COMPRESS OBFUSCATION - PowerShell
Status: test
Description:Detects Obfuscated Powershell via COMPRESS OBFUSCATION
References:
  -https://github.com/SigmaHQ/sigma/issues/1009
Author: Timur Zinniatullin, oscd.community
Date: 2020-10-18
modified:2022-11-29
Tags:

• -'attack.stealth'
• -'attack.t1027'
• -'attack.execution'
• -'attack.t1059.001'

Logsource:

• product: windows
• category: ps_script
• definition: Requirements: Script Block Logging must be enabled

Detection:
  selection_4104:
    ScriptBlockText|contains|all:
      -'new-object'
      -'text.encoding]::ascii'

    ScriptBlockText|contains:
      -'system.io.compression.deflatestream'
      -'system.io.streamreader'

    ScriptBlockText|endswith: 'readtoend'
  condition:selection_4104
Falsepositives:
  -Unknown
Level: medium