In the course of reviewing a number of published threat models, it became apparent that there is not (nor does there need to be) any standard output format, even given the same methodology (e.g., STRIDE).
I’m into spreadsheets. Applying structure to data in a tabular format makes it possible to sort, summarize, use math and statistics to glean insights, and generally makes data more portable. So, I started collecting threat modeling outputs that fit into columns and rows, and I put them in into a Google Sheet.
For now, the template includes the following output formats:
Shostack, from Table 1-3 Addressing Repudiation Threats in the canonical reference Threat Modeling: Designing for Security. The primary dimensions here are Threat Target, Mitigation Strategy, and Mitigation Technique.
Sysdig, from ECS Fargate threat modeling. This uses Asset, Threat, Security Control, and Mitigation Strategy as outputs.
Riggle, from An introduction to approachable threat modeling. This uses Principles, Goals, Adversaries, and Invariants as the entities in the model.