Sigma rule: Powershell Token Obfuscation - Powershell

Rule

Title

Powershell Token Obfuscation - Powershell

Status

test

Level

medium

Author

frack113

Date

2022-12-27

Modified

2025-10-19

File

rules-threat-hunting/windows/powershell/powershell_script/posh_ps_token_obfuscation.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects TOKEN OBFUSCATION technique from Invoke-Obfuscation in Powershell scripts.
Use this rule as a threat-hunting baseline to find obfuscated scripts in your environment.
Once tested and tuned, consider deploying a production detection rule based on this hunting rule.

Log source

product

windows

category

ps_script

definition

Requirements: Script Block Logging must be enabled

Detection

selection:
    # Examples:
    #   IN`V`o`Ke-eXp`ResSIOn (Ne`W-ob`ject Net.WebClient).DownloadString
    #   &('In'+'voke-Expressi'+'o'+'n') (.('New-Ob'+'jec'+'t') Net.WebClient).DownloadString
    #   &("{2}{3}{0}{4}{1}"-f 'e','Expression','I','nvok','-') (&("{0}{1}{2}"-f'N','ew-O','bject') Net.WebClient).DownloadString
    - ScriptBlockText|re: '\w+`(\w+|-|.)`[\w+|\s]'
    # - ScriptBlockText|re: '\((\'(\w|-|\.)+\'\+)+\'(\w|-|\.)+\'\)' TODO: fixme
    - ScriptBlockText|re: '"(\{\d\}){2,}"\s*-f'  # trigger on at least two placeholders. One might be used for legitimate string formatting
    #   ${e`Nv:pATh}
    - ScriptBlockText|re: '(?i)\$\{`?e`?n`?v`?:`?p`?a`?t`?h`?\}'
filter_envpath:
    ScriptBlockText|contains: '${env:path}' # TODO: Fix this. See https://github.com/SigmaHQ/sigma/pull/4964
filter_chocolatey:
    ScriptBlockText|contains:
        - 'it will return true or false instead'  # Chocolatey install script https://github.com/chocolatey/chocolatey
        - 'The function also prevents `Get-ItemProperty` from failing' # https://docs.chocolatey.org/en-us/create/functions/get-uninstallregistrykey
filter_exchange:
    Path|startswith: 'C:\Program Files\Microsoft\Exchange Server\'
    Path|endswith: '\bin\servicecontrol.ps1'
    ScriptBlockText|contains: '`r`n'
condition: selection and not 1 of filter_*

False positives (as the rule lists them)

• Edge case might be possible with heavy use of string formatting or obfuscation in legitimate scripts.

Tags

• attack.stealth
• attack.t1027.009
• detection.threat-hunting

MITRE ATT&CK ids this rule names

• T1027.009

Related rules

• deb9b646-a508-44ee-b7c9-d8965921c6b6 (similar)

References

• https://github.com/danielbohannon/Invoke-Obfuscation

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