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Suspicious PowerShell Script Block Invocations Using Encoded/Hidden Execution and Persistence Commands

Flags PowerShell script blocks using hidden/non-interactive execution, encoded/decode patterns, iex execution, web downloads, or run key modifications.

FreeReviewedSigma · High · v2
Product
windows
Category
ps_script
Author
Florian Roth (Nextron Systems), Jonhnathan Ribeiro (SigmaHQ), DRL 1.1
Published
2017-03-05
Updated
2026-07-31
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 PowerShell script block content that includes execution patterns commonly used to run code covertly, such as hidden windows, execution policy bypass, encoded payload handling, and base64-to-bytes decoding with Convert.FromBase64String. It also matches script blocks that combine web download techniques with iex/New-Object usage and those that attempt to establish persistence by modifying common Run registry keys. The detection relies on Script Block Logging telemetry (ScriptBlockText) to match specific parameter and command substrings within PowerShell activity.

Reporting behind it

Related detections9 linkedT1059.001 — drag to rearrange
Suspicious Script Interpreter Spawned by Explorer via ClickFix Run Dialog (via process_creation)
Suspicious PowerShell Download Cradle via ClickFix Fake CAPTCHA (via process_creation)
Suspicious PowerShell EncodedCommand Spawned From Command Shell via Process Creation
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
Suspicious PowerShell Script Block Invocations Using Encoded/Hidden Execution and Persistence Commands
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.