huntrule

Windows PowerShell Command Line Encoded-Content Indicators via Type Conversion and String Building

Detects PowerShell command lines containing type-conversion and join/split character assembly indicators consistent with encoded content handling.

FreeReviewedSigma · Low · v1
Product
windows
Category
process_creation
Author
Teymur Kheirkhabarov (idea), Vasiliy Burov (rule), oscd.community, Tim Shelton (SigmaHQ), DRL 1.1
Published
2020-10-11
Updated
2026-07-30
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 process creation events where the executable is PowerShell (powershell.exe or pwsh.exe) and the command line includes specific method names consistent with encoded or transformed content handling (e.g., ToInt/ToDecimal/ToByte/ToString). It also looks for string construction patterns using combinations of 'char' with 'join' or 'split' with 'join'. Attackers often use PowerShell command-line encoding and transformation to obscure payloads and evade casual inspection, making these command-line telemetry fields valuable for detection.

Reporting behind it

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Windows PowerShell Command Line Encoded-Content Indicators via Type Conversion and String Building
Pivot detection · T1027 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.