PowerShell ConvertTo-SecureString Cmdlet Execution from Command Line (Windows)

Alerts when PowerShell is launched with a command line containing ConvertTo-SecureString, a credential-related cmdlet uncommon in normal execution.

FreeReviewedSigma · Medium · v1

Product: windows
Category: process_creation
Author: Teymur Kheirkhabarov (idea), Vasiliy Burov (rule), oscd.community, Tim Shelton (SigmaHQ), DRL 1.1
Published: 2020-10-11
Updated: 2026-07-30

Analysis Detection

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1059.001PowerShell
Persistence
Priv Esc
Defense Evasion
- T1027Obfuscated Files or Information
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule identifies process executions of PowerShell (powershell.exe or pwsh.exe) where the command line contains the ConvertTo-SecureString cmdlet. Attackers may use this cmdlet to handle credentials or reduce the visibility of sensitive values during PowerShell-driven actions. The detection relies on process creation telemetry, specifically the process image path and the command-line string.

Reporting behind it

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PowerShell ConvertTo-SecureString Cmdlet Execution from Command Line (Windows)

Pivot detection · T1027 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

powershell-convertto-securestring-cmdlet-execution-from-command-line-windows-74403157

title: PowerShell ConvertTo-SecureString Cmdlet Execution from Command Line (Windows)
id: d3cb4a14-ca4d-4d38-9062-17617f269a44
status: test
description: This rule identifies process executions of PowerShell (powershell.exe or pwsh.exe) where the command line contains the ConvertTo-SecureString cmdlet. Attackers may use this cmdlet to handle credentials or reduce the visibility of sensitive values during PowerShell-driven actions. The detection relies on process creation telemetry, specifically the process image path and the command-line string.
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
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_powershell_cmdline_convertto_securestring.yml
author: Teymur Kheirkhabarov (idea), Vasiliy Burov (rule), oscd.community, Tim Shelton, Huntrule Team
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
license: DRL-1.1
related:
  - id: 74403157-20f5-415d-89a7-c505779585cf
    type: derived

Convert

This rule as a query you can run. Uses no unlock credit.

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