# Johan Brissmyr

> Johan Brissmyr is the CEO and co-founder of Castle, a security company that helps online businesses detect fraud, bots, and account takeover in real time. A computer scientist from Lund University, he started building web products in Malmo, Sweden before moving to Silicon Valley through Y Combinator and relocating the company to New York. Castle grew out of a password-storage side project that revealed a bigger opportunity in behavioral risk scoring, and today combines device fingerprinting, behavioral signals, and analytics into APIs used by companies of many sizes.

- **Role:** CEO & Co-founder at Castle
- **Organizations:** Castle, Userbin, SettleBox, Popdevelop, ARM
- **From:** Sweden
- **Nationality:** Swedish
- **Education:** Master of Science in Computer Science, Lund University, Faculty of Engineering (LTH)
- **Known for:** Co-founded and leads Castle, a real-time fraud and account-takeover detection platform, Graduated Y Combinator (W2016) after two prior rejections, Raised roughly $11.8M in total funding for Castle, including a Series A

## Career timeline

- **2005** — Earns MSc in Computer Science from Lund University's Faculty of Engineering
- **2000s** — Works at ARM before turning to startups
- **2000s** — Co-founds Popdevelop, a web development shop in Sweden, after leaving a large company
- **2010s** — Co-founds SettleBox, a portable digital identity for online marketplaces, as CTO
- **2010s** — Co-founds and leads Userbin, authentication as a service for consumer apps
- **2015** — Founds Castle in Malmo, Sweden with Sebastian Wallin, pivoting from password storage to fraud detection
- **2016** — Castle graduates from Y Combinator (Winter 2016) after being accepted on the third application
- **2019** — Castle raises a Series A; total funding reaches roughly $11.8M
- **2020s** — Leads Castle from New York as CEO, expanding device intelligence and behavioral risk products

## Achievements

- Co-founded and leads Castle, a real-time fraud and account-takeover detection platform
- Graduated Y Combinator (W2016) after two prior rejections
- Raised roughly $11.8M in total funding for Castle, including a Series A
- Built multiple identity and authentication startups (Userbin, SettleBox) before Castle
- Relocated a Swedish startup to Silicon Valley and then New York, scaling to ~50 employees

## Latest updates

- **2019-02** — Castle closed a Series A round, bringing total funding to roughly $11.8M
- **2023-07** — Highlighted Castle's integration with Twilio Segment for instant account protection signals

## Links

- Website: https://castle.io
- LinkedIn: http://www.linkedin.com/in/brissmyr
- Twitter/X: http://twitter.com/brissmyr
- GitHub: https://github.com/brissmyr
- Instagram: https://www.instagram.com/brissmyr/
- Facebook: https://facebook.com/WeAreCastle/

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Profile page: https://yespress.io/johan-brissmyr
Published by YesPress — https://yespress.io
Last updated: 2026-07-16