Arjen Lentz started programming as a teenager in the early ’80s, using a PDP-8 at the local computer club and an Acorn BBC/B at home, where he also tinkered with electronics. These were the days when computers did nothing unless you coded them yourself, so he explored (dis)assembly, bulletin boards, and modems. However, recognising the limited legal career opportunities in those areas, he shifted his focus to C programming as a profession, making use of his data communications and low-level programming skills.

Beyond custom projects for clients, Arjen wrote and refactored significant portions of code for the BBS and FidoNet community. His work included:
- The Xenia Mailer (based on The-Box by his friend Jac Kersing),
- The Xenia Email reader and editor,
- A fresh implementation of Zmodem to improve connections over unreliable satellite links, preventing costly protocol deadlocks (along the way, he identified a key design flaw in the protocol that caused those deadlocks),
- The Hydra bidirectional file transfer protocol, designed to make the most of the bandwidth offered by high-speed V.32bis modems.

When OS/2 arrived, Arjen embraced it eagerly, as (Double)DOS could only do so much. OS/2 Warp (GUI quirks aside) was a solid environment, as was the Watcom C/C++ compiler. Later, Slackware Linux arrived by post from Walnut Creek on CDs. Code from that era occasionally appears on github.com/lentzdev, mostly for nostalgia but sometimes still useful.

Around the turn of the millennium, Arjen moved to Australia, attracted by the space, climate, and new opportunities. Some time afterward, he joined MySQL as employee #25, working remotely for the ambitious startup. Some may remember him from this period, particularly for his talk at the NLUUG Voorjaarsconferentie 2003, where Bram Molenaar chaired the programme. Arjen’s afternoon presentation explained how MySQL managed to build a profitable business while giving away its software for free.

After his time at MySQL, Arjen ran his own training and consulting business for 11 years before selling it and returning to the security field as a CISO. It turned out he had simply been ahead of his time: the market for security skills had yet to mature. Now, we all know that market is thriving, and coding experience is a fantastic additional asset, as is an understanding of how businesses work.

Today, while Arjen occasionally codes, he serves as Senior Technical Architect at Ravinn, a Queensland-based boutique cybersecurity company. He has a particular interest in fundamentally improving security. Last year, Arjen found and fixed a security bug in sudo.

Arjen doesn’t blog much these days but scribbles his opinions on:
- LinkedIn
- Mastodon: @arjenlentz@mastodon.social and @art461@infosec.exchange

He is dedicated to open source, most recently acting as treasurer for the Everything Open 2026 conference in Canberra.

Bart is a Flutter software developer in his daily life and a core team member of postmarketOS and package maintainer for Alpine Linux. He is interested in anything Linux desktop and phone related and is active in the KDE community. He maintains the KDE stack, including Plasma Desktop and Mobile, for both postmarketOS and Alpine Linux and likes talking about this with a lot of passion. He can often be found at events like FOSDEM and KDE's Akademy.

Curious Troublemaker. Occasionally useful. Persistent tinkerer turned boundary spanner, uniting the hacker community with public policymakers and safety-critical industries. Helped stand up I Am The Cavalry, Hackers on the Hill, ICS Village, Aerospace Village, Biohacking Village: Device Lab, and Policy @ DEF CON. Has advised Congress, the White House, and governments around the world (and yes, they actually listened sometimes).

Frank van Vliet has more than 20 years of hands-on experience in cybersecurity and is known as one of the best ethical hackers in the Netherlands. Frank started his impressive cybersecurity career as a security penetration tester and software auditor.

Frank co-founded Certified Secure in 2007 and is currently the Chief Technology Officer (CTO), overseeing all Certified Secure trainings. Frank’s famous slogan “What could possibly go wrong”, has kick-started the Hacker Mindset of thousands of trainees world-wide. If you are hiring senior engineers, chances are they have been trained by Frank.

Jacco Brouwer is werkzaam voor de Vereniging Nederlandse Gemeenten als beleidscoördinator Cloud en Digitalisering, lid van het NDS Aanjaagteam op Cloud en de programmeringstafel Infrastructuur van het programma pGDI. Jacco tevens initiatiefnemer van de publieke Incubator GROEI waarmee VNG gemeentelijke samenwerking en innovatie vanuit een startup filosofie begeleiden bij de opschaling naar breed en collectief gebruik onder gemeenten en collega overheden.

Jan-Piet is an independent Unix/Linux consultant and sysadmin who's worked with Unix-systems since 1985.

JP does odd bits of coding, and works extensively with the Domain Name System and as such, he authored the book Alternative DNS Servers as well as a variety of other technical publications. He contributed several modules and the documentation system to the Ansible project and dreamed up the Open Source (MQTT-based) OwnTracks project. JP blogs at jpmens.net

1984-1990 Software Engineer bij KPMG
1990-2010 docent/cursusontwikkelaar bij AT Computing
2010-2026 Site Rilaibility Engineer bij Google Zürich

1995-2007 Bestuurslid NLUUG, waarvan 2000-2006 als voorzitter

Jeroen Baten is an open-source developer and IT coach with 25+ years of experience in Linux, CI/CD, and web application development. He contributes to the LibrePlan project, where he recently migrated all GitHub-based workflows to Forgejo Actions. He helps organizations adopt open-source tooling and build digitally autonomous development infrastructures.

Jeroen van der Ham-de Vos (he/him) is associate professor of Cyber Security Vulnerability Management at the University of Twente. His research currently focuses on vulnerability prioritisation and management, incdent response, the many developments in coordinated vulnerability disclosure and ethics of cybersecurity and computer science.
Jeroen has worked at the National Cyber Security Centre-NL from 2015 until 2023 as a cybersecurity researcher. There he coordinated the NCSC Research Agenda, was the national expert on Coordinated Vulnerability Disclosure, and was part of crisis teams such as with Wannacry or Log4J.

Jessica Tran is sinds een jaar of 6 oud met computers bezig, en al jaren Linux gebruiker. Ze is opgeleid tot software engineer, maar gezien ze meer plezier had in security & sysadmin taken heeft ze de overstap gemaakt en werkt ze tegenwoordig als Security & Compliance Officer bij team.blue. Tevens spreekt ze zich op privetitel uit over privacy en digitale sovereigniteit. In haar vrije tijd houd ze zich bezig met privacy, security, gamen, mensachtige-AI & HRI en eigenlijk alles omtrent computers. Daarnaast heeft ze een grote liefde voor honden en paarden, en het verzamelen van CDs.

Jessica is te vinden op haar persoonlijke website https://cambionn.nl of op Mastodon als @Cambion@mastodon.nl (https://mastodon.nl/@Cambion).

Dr. Jon Sneyers is a Staff Researcher at Cloudinary, a company providing cloud-based image and video management services to a million web developers at thousands of companies. His research focuses on image processing and image compression. He is the co-creator of the FLIF and JPEG XL image formats, an active participant in the JPEG committee and an editor of the ISO/IEC 18181 standard (JPEG XL) and the ISO/IEC 29170-3 standard (Subjective quality assessment of high-fidelity images, JPEG AIC-3).

Bio: Katie Trimble-Noble
Director, PSIRT and Bug Bounty 
Katie serves as a CVE Program Board, Bug Bounty Community of Interest Founder, and Hacking Policy Council Founding member. She is a passionate defensive cybersecurity community activist, she is regularly involved is community driven projects and is most happy when she is able to effect positive progress in cyber defense. In her day job Katie Noble serves as a Director of PSIRT, specializing in Global Secretarial Policy and Industry Engagement and Bug Bounty, at a fortune 50 Technology Company. Prior to joining private sector, Katie spent over 15 years in the US Government. Most recently as the Section Chief of Vulnerability Management and Coordination at the Department of Homeland Security, Cyber and Infrastructure Security Agency (CISA). Her team is credited with the coordination and public disclosure of 20,000+ cybersecurity vulnerabilities within a two-year period. During her government tenure, in roles spanning Intelligence Analyst for the National Intelligence Community to Senior Policy Advisor for White House led National Security Council Cyber programs, Katie’s work directly impacted decision making for government agencies in the United States, United Kingdom, Canada, and Australia.

Marcel-Jan Krijgsman is a senior data engineer with 27 years experience in data. Learning Python when switching his career to data engineering 9 years ago, these days it's part of his daily life. Whether he retrieves data from his weighing scale to store in a database, or updating his cycling dashboard on an e-ink display.

Architect for SME-businesses to automate processes. Currently involved with AI projects to automate the production of doorframes, record keeping of governmental debt-consultants, and automated Energy-label creation.

Niels Hatzmann werkt voor de Kiesraad in het team dat Abacus bouwt, de nieuwe uitslagensoftware. Eerder was hij als projectleider en documentatiespecialist betrokken bij het programma Realisatie Digitale Ondersteuning van het Ministerie van VWS en werkte hij als onderzoeker samen met Stratix aan adviezen op het gebied van digitale infrastructuur.

Victor Julien is a Dutch developer who has been developing open source security software for over 20 years. As the original creator and current lead developer of Suricata he has been doing Open Source development professionally for over 15 years. For OISF Victor is leading an international development team and frequently speaks about Suricata at conferences including Suricata's own annual conference Suricon.

Victor is living and working in Amsterdam, the Netherlands.

Als Linux/Open Source consultant en trainer bij AT Computing heb ik een bijzondere belangstelling voor Linux, Open Source en Security. Behalve het geven van een security awareness trainigen richt ik mijn aandacht graag op de technische beveiliging van Linuxsystemen zoals bijvoorbeeld implementatie van CIS Level II, Identity Management of aanscherping van privileged access management.

In mijn dagelijkse praktijk als Linux consultant zie ik helaas maar al te vaak hoe secrets zoals privésleutels of wachtwoorden uit Linuxsystemen en -applicaties ontfutselt kunnen worden. Met behulp van TPM en standaard Linux tools (!) kan diefstal echter zinloos worden gemaakt omdat de gestolen secrets op andere computers onbruikbaar zijn.

Met ruim 25 jaar Unix en Linux ervaring in grote organisaties wil ik deze kennis graag delen op de NLUUG conferentie!