I couldn't run Microsoft's Threat Modeling Tool on my Mac, so I rebuilt it for the browser

Description and use

The author built ThreatSketch, a browser‑based tool that reproduces Microsoft Threat Modeling Tool’s threat generation on macOS, Windows, and Linux, reducing download and install size while keeping file compatibility.

Problem

Microsoft's Threat Modeling Tool (TMT) only runs on Windows, preventing macOS users from using it in a cybersecurity course.

Outcome

ThreatSketch delivers TMT’s threat generation in a lightweight, cross‑platform browser app, reducing download size from 100 MB to 22 MB and installation size from 236 MB to 44 MB, while maintaining compatibility with Threat Dragon files and TMT workflows.

Workflow

• Draw a data‑flow diagram in ThreatSketch (or Threat Dragon)
• The Python engine (via Pyodide) parses the TMT .tb7 template and evaluates its rules
• The engine determines trust boundaries and generates threats
• Threats are merged into the model without overwriting edits
• Students triage threats, export reports, and save .tm7 files

Evidence

TMT only runs on Windows

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ThreatSketch saves Threat Dragon's JSON, so a model still opens in Threat Dragon

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The Python engine runs unchanged in the browser through Pyodide

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ThreatSketch 0.6 download 22 MB, installed 44 MB vs Threat Dragon 100 MB download, 236 MB installed

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