PowerShell Crypto Namespace Class Invocation for Windows Process Creation

Alerts on PowerShell executions that reference System.Security.Cryptography and common crypto class names.

FreeReviewedSigma · Medium · v5

Product: windows
Category: process_creation
Author: Andreas Braathen (mnemonic.io) (SigmaHQ), DRL 1.1
Published: 2023-12-01
Updated: 2026-07-31

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1059.001PowerShell
Persistence
Priv Esc
Defense Evasion
- T1027.010Command Obfuscation
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags Windows process creation events where PowerShell (powershell.exe or pwsh.exe) is launched with command-line content referencing the System.Security.Cryptography namespace and specific cryptography class names. Attackers may use built-in .NET cryptography APIs to perform on-the-fly decryption or encryption during execution for stealth and payload handling. The detection relies on process creation telemetry containing the process image and the full command line text.

Reporting behind it

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Suspicious PowerShell Download Cradle via ClickFix Fake CAPTCHA (via process_creation)

Suspicious PowerShell EncodedCommand Spawned From Command Shell via Process Creation

Suspicious Script Download via Curl and PowerShell by Dohdoor

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Suspicious PowerShell WebClient DownloadFile of Archive Payload (UAT-7237)

PowerShell Crypto Namespace Class Invocation for Windows Process Creation

Pivot detection · T1059.001 · 9 related

Changelog

v5
Candidate ingested via manual entry.2026-07-31
v4
Candidate ingested via manual entry.2026-07-31
v3
Candidate ingested via manual entry.2026-07-31
v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

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

powershell-process-command-line-uses-system-security-cryptography-classes-ad856965

title: PowerShell Crypto Namespace Class Invocation for Windows Process Creation
id: 4d1f81dc-87e5-4b69-b5be-c2736e28a7a1
status: test
description: This rule flags Windows process creation events where PowerShell (powershell.exe or pwsh.exe) is launched with command-line content referencing the System.Security.Cryptography namespace and specific cryptography class names. Attackers may use built-in .NET cryptography APIs to perform on-the-fly decryption or encryption during execution for stealth and payload handling. The detection relies on process creation telemetry containing the process image and the full command line text.
references:
  - https://learn.microsoft.com/en-us/dotnet/api/system.security.cryptography?view=net-8.0
  - https://blogs.vmware.com/security/2023/11/jupyter-rising-an-update-on-jupyter-infostealer.html
  - https://www.virustotal.com/gui/file/39102fb7bb6a74a9c8cb6d46419f9015b381199ea8524c1376672b30fffd69d2
  - https://github.com/SigmaHQ/sigma/blob/master/rules-threat-hunting/windows/process_creation/proc_creation_win_powershell_crypto_namespace.yml
author: Andreas Braathen (mnemonic.io), Huntrule Team
date: 2023-12-01
tags:
  - attack.execution
  - attack.stealth
  - attack.t1059.001
  - attack.t1027.010
  - detection.threat-hunting
logsource:
  product: windows
  category: process_creation
detection:
  selection_img:
    - Image|endswith:
        - \powershell.exe
        - \pwsh.exe
    - OriginalFileName:
        - PowerShell.EXE
        - pwsh.dll
  selection_cmdlet_namespace:
    CommandLine|contains: System.Security.Cryptography.
  selection_cmdlet_classes:
    CommandLine|contains:
      - .AesCryptoServiceProvider
      - .DESCryptoServiceProvider
      - .DSACryptoServiceProvider
      - .RC2CryptoServiceProvider
      - .Rijndael
      - .RSACryptoServiceProvider
      - .TripleDESCryptoServiceProvider
  condition: all of selection_*
falsepositives:
  - Classes are legitimately used, but less so when e.g. parents with low prevalence or decryption of content in temporary folders.
level: medium
license: DRL-1.1
related:
  - id: ad856965-f44d-42a8-945e-bbf7bd03d05a
    type: derived

Convert

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

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