huntrule

Windows PowerShell detects obfuscated Net.Webclient casing anomalies in command line

Alerts when PowerShell command lines contain encoded obfuscation patterns referencing Net.Webclient with anomalous casing.

FreeReviewedSigma · High · v1
Product
windows
Category
process_creation
Author
Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2022-05-24
Updated
2026-07-30
AnalysisDetection

ATT&CK techniques

Execution

  1. Recon

  2. Resource Dev

  3. Initial Access

  4. Execution

  5. Persistence

  6. Priv Esc

  7. Defense Evasion

  8. Cred Access

  9. Discovery

  10. Lateral Movement

  11. Collection

  12. C2

  13. Exfiltration

  14. Impact

What it detects

This rule flags Windows process creations where PowerShell or pwsh is used and the command line contains encoded fragments consistent with obfuscation plus an abnormal mixed-case reference to Net.Webclient. Attackers commonly vary casing to evade simple string-based detections, including around commonly abused .NET types used for web requests. Telemetry required includes process creation events with process image path/name and the full PowerShell command line content.

Reporting behind it

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Suspicious PowerShell WebClient DownloadFile of Archive Payload (UAT-7237)
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Suspicious Python Interpreter Launching Encoded PowerShell via subprocess
Windows PowerShell detects obfuscated Net.Webclient casing anomalies in command line
Pivot detection · T1059.001 · 9 related

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