huntrule

Windows PowerShell Base64-encoded shellcode in ScriptBlockText

Flags PowerShell script blocks containing Base64 strings matching known shellcode markers.

FreeReviewedSigma · High · v2
Product
windows
Category
ps_script
Author
David Ledbetter (shellcode), Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
Published
2018-11-17
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 contains specific Base64-encoded sequences associated with embedded shellcode. Attackers may use Base64 to conceal payloads within otherwise normal-looking PowerShell execution, aiming to increase stealth. The detection relies on Script Block Logging telemetry by matching the presence of the defined encoded markers in the captured ScriptBlockText.

Reporting behind it

Related detections9 linkedT1059.001 — drag to rearrange
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Suspicious Script Download via Curl and PowerShell by Dohdoor
Malicious Mass Hyper-V Virtual Machine Shutdown via PowerShell by Kraken Ransomware
Suspicious PowerShell WebClient DownloadFile of Archive Payload (UAT-7237)
Suspicious SharePoint Worker Process Spawning Command Interpreter via ToolShell
Malicious Emmenhtal JavaScript Loader Spawning Encoded PowerShell
Suspicious Python Interpreter Launching Encoded PowerShell via subprocess
Windows PowerShell Base64-encoded shellcode in ScriptBlockText
Pivot detection · T1059.001 · 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.