huntrule

PowerShell: Obfuscated invocation via Environment Variables in Script Block

Alerts on PowerShell script blocks launching cmd /c or /r with obfuscated set-and-{n} variable expansion patterns.

FreeReviewedSigma · High · v2
Product
windows
Category
ps_script
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 PowerShell script block content that constructs command execution using environment variable expansion in an obfuscated manner. Attackers use this pattern to hide the executed command and evade casual inspection while still relying on standard PowerShell and command invocation semantics. It relies on PowerShell Script Block logging telemetry to match suspicious script block text patterns containing the obfuscated cmd/cmd /r logic and set-variable usage.

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)
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PowerShell: Obfuscated invocation via Environment Variables in Script Block
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.