huntrule

Windows PowerShell CommandLine downloads and executes via WebClient with IEX or DownloadFile

Alerts on PowerShell command lines that use WebClient downloads combined with IEX or DownloadFile, typical of staged payload execution.

FreeReviewedSigma · High · v1
Product
windows
Category
process_creation
Author
Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2022-02-28
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 creation where the PowerShell command line includes suspicious download-and-execute patterns using WebClient combined with IEX and DownloadString/DownloadFile. Attackers commonly use these techniques to stage payloads by fetching code or files from remote locations and immediately executing them in memory or via a downloaded artifact. It relies on process_creation telemetry capturing the full PowerShell command line and matching specific substrings indicative of this behavior.

Reporting behind it

Related detections9 linkedT1059.001 — drag to rearrange
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Suspicious PowerShell WebClient DownloadFile of Archive Payload (UAT-7237)
Suspicious SharePoint Worker Process Spawning Command Interpreter via ToolShell
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Suspicious Python Interpreter Launching Encoded PowerShell via subprocess
Windows PowerShell CommandLine downloads and executes via WebClient with IEX or DownloadFile
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.