CAIRIS

CAIRIS is an open-source platform for developing and assessing secure, usable systems. It best suits teams that need requirements, user perspectives, architecture, and security analysis to inform one another. Its broad modeling and documentation capabilities come with a practical caveat: the public demo exposes its databases and is rebuilt nightly.

Overview

CAIRIS brings security, usability, and requirements data into a shared design, covering assets, countermeasures, factoids, personas, requirements, and architectural components. That integrated scope helps teams assess security alongside the people and requirements a system must serve. It is a better fit for structured design work than for teams seeking only a quick threat diagram.

The platform can generate 12 views of an evolving design, covering perspectives such as people, risks, requirements, architecture, and physical location. It can also produce threat models, including Data Flow Diagrams, as a design develops. These outputs can help keep review aligned with design changes, while their usefulness depends on the model being accurate and current.

Key features

Threat and security analysis

CAIRIS supports multiple modeling methods, attack-path analysis, and risk prioritization. Attack and architectural patterns help assess attack surface and validate designs for known security problems and potential GDPR compliance issues. This combination is useful when security analysis needs to shape architecture early, rather than follow it as a separate exercise.

Documentation and integration

It can generate Volere-compliant requirement specifications and GDPR DPIA documents, giving teams a route from modeled design work to formal deliverables. The API can support custom design applications or integration with an existing toolchain. Collaborative review and templates and frameworks are also supported, though the supplied plan details do not define collaboration or template limits.

The Persona Helper Chrome Extension can turn highlighted web-page text into document references connected to a CAIRIS server. That is a focused aid for gathering persona-related references, not a substitute for the broader modeling workflow.

Pricing

CAIRIS is free: its Free plan costs nothing and is freely available under the Apache Software License. There is no paid tier to compare or upgrade to, making it a straightforward option for teams able to deploy and operate it themselves. The plan details do not give seat or quota caps.

The live demo is convenient for evaluation, but it is not an appropriate home for confidential or durable work. Its databases are visible to everyone, the container is rebuilt nightly, and accounts other than the recreated test account are deleted on Sunday morning each week. Export models to retain work before a rebuild; use an installation you control for sensitive projects.

Platforms

CAIRIS supports API access and runs across Linux, macOS, Windows, web, and self-hosted environments. It can be installed with Docker or Vagrant, or built from source on platforms supported by its open-source dependencies; Ubuntu is the most tested platform. The browser application supports modern browsers, including Microsoft Edge, but not Internet Explorer. This breadth gives teams deployment options, while the stronger testing focus on Ubuntu makes it the most defensible starting point for self-hosting.

Who it's for

Choose CAIRIS if your work needs to connect requirements, personas, architecture, threat models, and security documentation in a single design process. Its range is particularly relevant to teams that need attack-path analysis, risk prioritization, and outputs such as requirement specifications or DPIAs. Look elsewhere if you need a low-friction diagramming tool or a public demo in which project data can remain private.

Pros and cons

Integrated design scope: Security, usability, requirements, and architectural components share a model, supporting review across those concerns.

Useful generated outputs: Twelve design views, evolving threat models, requirement specifications, and DPIA documents can reduce the gap between analysis and deliverables.

Flexible deployment and integration: Docker, Vagrant, source installation, and an API support teams with different toolchains and hosting needs.

Demo privacy and persistence risks: Publicly visible databases and nightly rebuilds rule out treating the live demo as a confidential or reliable workspace.

Uneven platform confidence: Ubuntu is the most tested platform, so teams choosing another supported environment should account for that distinction.

Alternatives

Threat Modeling Software is a broader category directory for readers comparing approaches. OWASP Threat Dragon is another free, open-source option across Linux, macOS, self-hosted, web, and Windows; choose it when you want a threat-modeling alternative without a stated paid tier or usage limit. ThreatOpus is worth considering when a team needs a web/API service with a defined Starter plan: £129.99 a month, with 15 users, 10 team workspaces, 50 threat modelling generations per month, and 10 repositories. AWS Threat Composer is another free option with broad platform support, including an extension, for readers comparing a different tool in this category.

ThreatModeler Nexus offers a free Community Edition aimed at practitioners, students, developers, architects, and security teams who want to explore threat modeling before scaling. ThreatTree has a capped free plan—up to 3 forests, 3 DFDs per forest, and 5 Attack Trees per DFD—and a Pro plan at $29 a month, billed per user monthly; consider it when those tree and diagram limits suit the work. IriusRisk offers a free Community Edition with 3 active threat models, one user with limited collaboration, templates and libraries, and XML diagram export, making it a fit when those stated caps and functions align with a project.

ThreatZ is another option for readers comparing threat-modeling products. CYMETRIS has a Lite plan at €99 a month, billed net €99/month, with one full TARA project included; consider it when a paid TARA project is a closer fit than CAIRIS's broader free modeling platform.

Verdict

CAIRIS is a strong choice for teams that want a free, open-source environment linking requirements and user perspectives with threat analysis, architecture, and formal security documentation. Its main advantage is that breadth; its main reason to look elsewhere is the effort and care required to deploy it, especially if the public demo seems like an easy shortcut. Keep confidential work on a controlled installation and export demo models before rebuilds.