SigmaHQ/rules/windows/powershell/powershell_invoke_obfuscation_obfuscated_iex.yml
2021-08-21 09:50:59 +02:00

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YAML

title: Invoke-Obfuscation Obfuscated IEX Invocation
id: 1b9dc62e-6e9e-42a3-8990-94d7a10007f7
description: "Detects all variations of obfuscated powershell IEX invocation code generated by Invoke-Obfuscation framework from the following code block \u2014 https://github.com/danielbohannon/Invoke-Obfuscation/blob/master/Out-ObfuscatedStringCommand.ps1#L873-L888"
status: experimental
author: Daniel Bohannon (@Mandiant/@FireEye), oscd.community
date: 2019/11/08
modified: 2020/08/24
tags:
- attack.defense_evasion
- attack.t1027
- attack.execution
- attack.t1059.001
- attack.t1086 #an old one
logsource:
product: windows
service: powershell
definition: Script block logging must be enabled for 4104, Module Logging must be enabled for 4103
detection:
selection_1:
EventID: 4104
selection_2:
- 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\('
- ScriptBlockText|re: '\String\]\s*\$VerbosePreference'
selection_3:
EventID: 4103
selection_4:
- Payload|re: '\$PSHome\[\s*\d{1,3}\s*\]\s*\+\s*\$PSHome\['
- Payload|re: '\$ShellId\[\s*\d{1,3}\s*\]\s*\+\s*\$ShellId\['
- Payload|re: '\$env:Public\[\s*\d{1,3}\s*\]\s*\+\s*\$env:Public\['
- Payload|re: '\$env:ComSpec\[(\s*\d{1,3}\s*,){2}'
- Payload|re: '\*mdr\*\W\s*\)\.Name'
- Payload|re: '\$VerbosePreference\.ToString\('
- Payload|re: '\String\]\s*\$VerbosePreference'
condition: ( selection_1 and selection_2 ) or ( selection_3 and selection_4 )
falsepositives:
- Unknown
level: high