Sigma rule: ConvertTo-SecureString Cmdlet Usage Via CommandLine

Rule

Title

ConvertTo-SecureString Cmdlet Usage Via CommandLine

Status

test

Level

medium

Author

Teymur Kheirkhabarov (idea), Vasiliy Burov (rule), oscd.community, Tim Shelton

Date

2020-10-11

Modified

2023-02-01

File

rules/windows/process_creation/proc_creation_win_powershell_cmdline_convertto_securestring.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

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

Log source

product

windows

category

process_creation

Detection

selection_img:
    - Image|endswith:
          - '\powershell.exe'
          - '\pwsh.exe'
    - OriginalFileName:
          - 'PowerShell.EXE'
          - 'pwsh.dll'
selection_cli:
    CommandLine|contains: 'ConvertTo-SecureString'
condition: all of selection_*

False positives (as the rule lists them)

• Legitimate use to pass password to different powershell commands

Tags

• attack.stealth
• attack.t1027
• attack.execution
• attack.t1059.001

MITRE ATT&CK ids this rule names

• T1027
• T1059.001

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

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_powershell_cmdline_convertto_securestring.yml