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Detection rules › Sigma

Invoke-Obfuscation VAR++ LAUNCHER OBFUSCATION - PowerShell

Status
test
Severity
high
Log source
category ps_script, product windows
Author
Timur Zinniatullin, oscd.community
Source
github.com/SigmaHQ/sigma

Detects Obfuscated Powershell via VAR++ LAUNCHER

MITRE ATT&CK coverage

TacticTechniques
Execution
Stealth

Telemetry coverage

ProviderRecord / event type
PowerShellEvent ID 4104: Creating Scriptblock text (MessageNumber of MessageTotal).

Rule body

title: Invoke-Obfuscation VAR++ LAUNCHER OBFUSCATION - PowerShell
id: e54f5149-6ba3-49cf-b153-070d24679126
status: test
description: Detects Obfuscated Powershell via VAR++ LAUNCHER
references:
    - https://github.com/SigmaHQ/sigma/issues/1009 # (Task27)
author: Timur Zinniatullin, oscd.community
date: 2020-10-13
modified: 2024-04-05
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|re: '(?i)&&set.*(\{\d\}){2,}\\"\s+?-f.*&&.*cmd.*/c' # FPs with |\/r
    condition: selection_4104
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: condition

selection_4104

Stage 1: selection_4104

selection_4104:
    ScriptBlockText|re: '(?i)&&set.*(\{\d\}){2,}\\"\s+?-f.*&&.*cmd.*/c'

Indicators

These rows show field, operator, and value matches.

FieldKindValuesSearch
ScriptBlockTextregex_match
  • (?i)&&set.*({\d}){2,}\"\s+?-f.*&&.*cmd.*/c
field:"ScriptBlockText" kind:regex_match