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Windows Process Creation: Cmd Invokes PowerShell via Obfuscated Environment Variable Expansion

Alerts on cmd.exe command lines that use obfuscated environment-variable SET to execute PowerShell.

FreeReviewedSigma · High · v2
Product
windows
Category
process_creation
Author
Jonathan Cheong, oscd.community (SigmaHQ), DRL 1.1
Published
2020-10-15
Updated
2026-07-31
AnalysisDetection

ATT&CK techniques

Execution → Defense Evasion

  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 command interpreter executions that use obfuscated environment variable expansion to construct and run PowerShell, matching a specific cmd /c or /r pattern containing a SET statement and encoded PowerShell invocation fragments. Such behavior matters because attackers often hide PowerShell payloads and reduce detection by dynamically building commands from environment variables. The detection relies on process creation telemetry, specifically the full CommandLine field for cmd.exe with the expected obfuscation characteristics.

Reporting behind it

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PowerShell Encoded or Download-Cradle Command Line (via process_creation)
Obfuscated Encoded PowerShell Payload Deployed - PowerShell (via powershell)
Suspicious PowerShell AES Decryption and Reflective Method Invocation in SolarMarker
Windows Process Creation: Cmd Invokes PowerShell via Obfuscated Environment Variable Expansion
Pivot detection · T1027 · 9 related

Changelog

v2
  1. v2
    Candidate ingested via manual entry.2026-07-31
  2. 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.