Twenty‑seven years at the sharp end of security.
I was a teenager when I started tracing virus writers for the FBI. Since then: penetration testing, national incident coordination, CSO at Klarna, expert witness before Swedish courts — and now Perseus Technology, building the next generation of forensics software.
Technical depth, translated for the people who decide.
The FBI came calling before I finished my teens — a Swedish kid helping trace the authors of Melissa and the Love Bug across the early internet. The instincts haven’t changed since. The stakes have.
Across a career spanning cybersecurity, digital forensics, security leadership, and education, I’ve worked every seat at the table — developer, penetration tester, founder, and Chief Security Officer of an international fintech. What I’m known for is translating complex technical reality into clear decisions for non-technical leadership.
I’ve coordinated national incidents, recruited and led security teams in sensitive environments, and delivered risk assessments grounded in hands-on technical analysis. Since 1999 I’ve worked in digital forensics, supporting law-enforcement investigations in Sweden and internationally, and I’m regularly engaged as an expert witness by lawyers, prosecutors, and Swedish district and appeals courts.
What drives me is making a difference — going the extra mile and delivering analysis that holds up under scrutiny. Deep expertise in OSINT, threat analysis, and the methods and patterns of real adversaries.
Selected roles, 1997 → today.
Finding the flaws before the adversary does.
Active in vulnerability research and coordinated disclosure — more than a hundred reports over the years, all disclosed directly to the affected vendors rather than through bug-bounty platforms, in a line of work that started with a Bugtraq advisory in 1999.
First public advisory
Published on the premier disclosure channel of its era
Read on SecLists ↗Perseus Technology
Specialist cybersecurity with forensic precision: digital forensics, incident response, wireless security research, and AI-driven security engineering — building groundbreaking DFIR software from the ground up.
perseustechnology.se ↗Two decades in the headlines.
Continuous learning.
Security Protection
Swedish Defence University (FHS)
Behaviour Analysis
Paul Ekman Institute / EIA Group
SANS FOR610
Reverse-Engineering Malware
Uppsala University
Political science, education, law, epistemology
Reverse Engineering
DataRescue, Liège, Belgium
Off the clock.
When I’m not working in security, I write and produce music.
For matters that need a lock.
Let’s talk.
Advisory, digital forensics, incident response, expert-witness engagements, teaching, or press — I read everything sent to this address.
jj@jonathanj.com