ConvertTo-SecureString Cmdlet Usage Via CommandLine

Detects usage of the "ConvertTo-SecureString" cmdlet via the commandline. Which is fairly uncommon and could indicate potential suspicious activity

title: ConvertTo-SecureString Cmdlet Usage Via CommandLine
id: 74403157-20f5-415d-89a7-c505779585cf
status: test
description: Detects usage of the "ConvertTo-SecureString" cmdlet via the commandline. Which is fairly uncommon and could indicate potential suspicious activity
references:
    - https://speakerdeck.com/heirhabarov/hunting-for-powershell-abuse?slide=65
    - https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.security/convertto-securestring?view=powershell-7.3#examples
author: Teymur Kheirkhabarov (idea), Vasiliy Burov (rule), oscd.community, Tim Shelton
date: 2020-10-11
modified: 2023-02-01
tags:
    - attack.stealth
    - attack.t1027
    - attack.execution
    - attack.t1059.001
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith:
              - '\powershell.exe'
              - '\pwsh.exe'
        - OriginalFileName:
              - 'PowerShell.EXE'
              - 'pwsh.dll'
    selection_cli:
        CommandLine|contains: 'ConvertTo-SecureString'
    condition: all of selection_*
falsepositives:
    - Legitimate use to pass password to different powershell commands
level: medium
regression_tests_path: regression_data/rules/windows/process_creation/proc_creation_win_powershell_cmdline_convertto_securestring/info.yml

• T1027Obfuscated Files or Information
• T1059.001PowerShell

• https://speakerdeck.com/heirhabarov/hunting-for-powershell-abuse?slide=65↗
• https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.security/convertto-securestring?view=powershell-7.3#examples↗