Sigma rule: Invoke-Obfuscation Obfuscated IEX Invocation - PowerShell

Rule

Title

Invoke-Obfuscation Obfuscated IEX Invocation - PowerShell

Status

test

Level

high

Author

Daniel Bohannon (@Mandiant/@FireEye), oscd.community

Date

2019-11-08

Modified

2022-12-31

File

rules/windows/powershell/powershell_script/posh_ps_invoke_obfuscation_obfuscated_iex.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects all variations of obfuscated powershell IEX invocation code generated by Invoke-Obfuscation framework from the following code block \u2014

Log source

product

windows

category

ps_script

definition

Requirements: Script Block Logging must be enabled

Detection

selection_iex:
    - ScriptBlockText|re: '\$PSHome\[\s*\d{1,3}\s*\]\s*\+\s*\$PSHome\['
    - ScriptBlockText|re: '\$ShellId\[\s*\d{1,3}\s*\]\s*\+\s*\$ShellId\['
    - ScriptBlockText|re: '\$env:Public\[\s*\d{1,3}\s*\]\s*\+\s*\$env:Public\['
    - ScriptBlockText|re: '\$env:ComSpec\[(\s*\d{1,3}\s*,){2}'
    - ScriptBlockText|re: '\*mdr\*\W\s*\)\.Name'
    - ScriptBlockText|re: '\$VerbosePreference\.ToString\('
condition: selection_iex

False positives (as the rule lists them)

• Unknown

Tags

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

MITRE ATT&CK ids this rule names

• T1027
• T1059.001

References

• https://github.com/danielbohannon/Invoke-Obfuscation/blob/f20e7f843edd0a3a7716736e9eddfa423395dd26/Out-ObfuscatedStringCommand.ps1#L873-L888

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/powershell/powershell_script/posh_ps_invoke_obfuscation_obfuscated_iex.yml