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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

Related detections9 linkedT1027 — drag to rearrange
Malicious FIN7 Powertrash Loader Execution via Obfuscated PowerShell (via process_creation)
Suspicious XOR Obfuscated PowerShell from ClickFix Distribution
Suspicious PowerShell Executing Code from Environment Variable (via process_creation)
Suspicious In-Memory Runspace Execution via PowerShell Script Block
Suspicious Encoded PowerShell Using Base64 Stream Decompression Routines (via process_creation)
Suspicious PowerShell In-Memory Execution with AES Decryption
Suspicious Encoded PowerShell Command Execution
Suspicious PEAKLIGHT Memory-Only PowerShell Downloader Flags (via process_creation)
Obfuscated PowerShell Script: Indirect Cmdlet Execution via ExportedCommands Array Index
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.