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Detection rules › Sigma

Powershell Token Obfuscation - Process Creation

Status
test
Severity
high
Log source
product windows, category process_creation
Author
frack113
Source
github.com/SigmaHQ/sigma

Detects TOKEN OBFUSCATION technique from Invoke-Obfuscation

MITRE ATT&CK coverage

TacticTechniques
StealthT1027.009 Obfuscated Files or Information: Embedded Payloads

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation
Security-AuditingEvent ID 4688A new process has been created.

Rule body yaml

title: Powershell Token Obfuscation - Process Creation
id: deb9b646-a508-44ee-b7c9-d8965921c6b6
related:
    - id: f3a98ce4-6164-4dd4-867c-4d83de7eca51
      type: similar
status: test
description: Detects TOKEN OBFUSCATION technique from Invoke-Obfuscation
references:
    - https://github.com/danielbohannon/Invoke-Obfuscation
author: frack113
date: 2022-12-27
modified: 2026-03-16
tags:
    - attack.stealth
    - attack.t1027.009
logsource:
    category: process_creation
    product: windows
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
        - CommandLine|re: '\w+`(?:\w+|-|.)`[\w+|\s]'
        # - CommandLine|re: '\((\'(\w|-|\.)+\'\+)+\'(\w|-|\.)+\'\)' TODO: fixme
        - CommandLine|re: '"(?:\{\d\})+"\s*-f'
        #   ${e`Nv:pATh}
        - CommandLine|re: '(?i)\$\{`?e`?n`?v`?:`?p`?a`?t`?h`?\}'
    filter_main_envpath:
        CommandLine|contains: '${env:path}'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection and not 1 of filter_main_*

Stage 1: selection

selection:
    - CommandLine|re: '\w+`(?:\w+|-|.)`[\w+|\s]'
    - CommandLine|re: '"(?:\{\d\})+"\s*-f'
    - CommandLine|re: '(?i)\$\{`?e`?n`?v`?:`?p`?a`?t`?h`?\}'

Stage 2: not filter_main_envpath

filter_main_envpath:
    CommandLine|contains: '${env:path}'

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

FieldKindExcluded values
CommandLinematch${env:path}

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
CommandLineregex_match
  • "(?:{\d})+"\s*-f
  • (?i)${`?e`?n`?v`?:`?p`?a`?t`?h`?}
  • \w+`(?:\w+|-|.)`[\w+|\s]