About

I’m Simon Mullis. Thirty years in cybersecurity, and my job title has never quite captured the work. Mostly I’ve worked in the field, as a sales engineer and solutions architect, but the whole time I’ve been doing the extra stuff too: writing the code, giving the talks, being the person sent in to explain the hard thing.

I’ve been coding for over twenty five years, from shell and object-oriented Perl (I’m not sorry) through Ruby and Python to a lot of Go and, lately, Rust. I’ve built and shipped enterprise SaaS, always with a team carrying half the weight. For five years I was CTO of Venari Security, a post-quantum cryptography startup, which is where I learned how much of security is an inventory problem wearing a maths costume.

I’ve spent a lot of time on the public-facing side too: press and media spokesperson for FireEye, Palo Alto Networks, Tanium, and Venari, and talks at TEDx Amsterdam, the European Council, and the European Parliament, plus a keynote at CyberCon Africa.

Today I’m a Principal Solutions Architect at SentinelOne. Much of my time goes to introducing AI and agentic systems across the organisation, working with our engineering, security, and IT teams on the internal tooling and the working practice. I won the company’s inaugural MCP Hackathon with a system that put fourteen agents to work using Go and LangChain. I still carry customer accounts, because staying close to the people who actually use this stuff is the point. What holds my attention now is the distance between an AI demo that works and a tool a regulated company can actually run in production. I write about that distance here, always starting from something I built or watched break. The understanding I trust most is the dilated, dropped-glass clarity of the instant before it shatters: the whole causal chain and its consequence arriving at once, uninvited and vivid.

I do the same work for other companies in advisory roles, and take on a small number of fractional-CTO engagements alongside. If that’s a fit for what you’re building, get in touch.

Originally from the UK, I live in Amsterdam, in the Netherlands.