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

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 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.