An opinionated selection of shapes to turn the free and cross-platform Excalibur diagramming application into the perfect tool for threat modeling. This repo is a backup of the shapes, saved as a flat file. The official Excalidraw Libraries repository will host the library.

Data Flow Diagramming is a simple diagramming technique used to gain an understanding of how data flows in an application or system. DFDs are excellent for getting a bird's-eye view of a system to facilitate threat modeling.

This library intentionally uses just five items:

• External entity: Anything outside your control. Examples include people and systems run by other organizations or even divisions.
• Process: Any running code, including compiled, scripts, shell commands, SQL stored procedures, et cetera.
• Data store: Anywhere data is stored, including files, databases, shared memory, S3, cookies, et cetera.
• Data flows: All the ways that processes can talk to data stores or each other.
• Trust boundary: It should be a closed shape, usually a box. Clearly show what's inside in a way that OG arcs often fail to do.

This was inspired by the good old Draw.io libraries for threat modeling by Michael Henriksen, with the goal to bring it in front of modern-age software engineers and "be where they are", not enforcing them to use [insert your tool of choice], when they want and use Excalidraw.

You may also find Adam Shostack's DFD3 useful, but I'm not too fond of drums for data stores and don't care enough about space efficiency in a large diagram to drop circles in favor of rounded rectangles... 🤷🏼‍♂️

• Open excalidraw.com (or install locally), click the Library button, and then click Browse Libraries;
• Search for Threat Modeling;
• Start diagramming!