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win_security_invoke_obfuscation_var_services_security.yml
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win_security_invoke_obfuscation_var_services_security.yml
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title: Invoke-Obfuscation VAR+ Launcher - Security
id: dcf2db1f-f091-425b-a821-c05875b8925a
related:
- id: 8ca7004b-e620-4ecb-870e-86129b5b8e75
type: derived
status: test
description: Detects Obfuscated use of Environment Variables to execute PowerShell
references:
- https://github.com/SigmaHQ/sigma/issues/1009 # (Task 24)
author: Jonathan Cheong, oscd.community
date: 2020/10/15
modified: 2022/11/29
tags:
- attack.defense_evasion
- attack.t1027
- attack.execution
- attack.t1059.001
logsource:
product: windows
service: security
definition: The 'System Security Extension' audit subcategory need to be enabled to log the EID 4697
detection:
selection:
EventID: 4697
# ServiceFileName|re: 'cmd.{0,5}(?:\/c|\/r)(?:\s|)\"set\s[a-zA-Z]{3,6}.*(?:\{\d\}){1,}\\\"\s+?\-f(?:.*\)){1,}.*\"'
# Example 1: C:\winDoWs\SySTeM32\cmd.Exe /C"SET NOtI=Invoke-Expression (New-Object Net.WebClient).DownloadString&& PowERshElL -NOl SET-iteM ( 'VAR' + 'i'+ 'A' + 'blE:Ao6' + 'I0') ( [TYpe](\"{2}{3}{0}{1}\"-F 'iRoN','mENT','e','nv') ) ; ${exECUtIONCOnTEXT}.\"IN`VO`KecOmMaND\".\"inVo`KES`crIPt\"( ( ( GEt-VAriAble ( 'a' + 'o6I0') -vaLU )::(\"{1}{4}{2}{3}{0}\" -f'e','gETenvIR','NtvaRIa','BL','ONme' ).Invoke(( \"{0}{1}\"-f'n','oti' ),( \"{0}{1}\" -f'pRoC','esS') )) )"
# Example 2: cMD.exe /C "seT SlDb=Invoke-Expression (New-Object Net.WebClient).DownloadString&& pOWErShell .(( ^&(\"{1}{0}{2}{3}\" -f 'eT-vaR','G','iab','lE' ) (\"{0}{1}\" -f '*m','DR*' ) ).\"na`ME\"[3,11,2]-JOIN'' ) ( ( ^&(\"{0}{1}\" -f'g','CI' ) (\"{0}{1}\" -f 'ENV',':SlDb' ) ).\"VA`luE\" ) "
ServiceFileName|contains|all:
- 'cmd'
- '"set'
- '-f'
ServiceFileName|contains:
- '/c'
- '/r'
condition: selection
falsepositives:
- Unknown
level: high