Hi There! 👋

My name is Arjen and I am the Manager of Product Development and Chief Lecturer at Hogeschool NOVI. I work on creating the most modern and relevant educational products that we can offer. Through stategic partnerships and attracting the most talented content developers we offer world class education to our students.

In my work as Chief Lecturer for Cybersecurity I focus on teaching students all there is to know about the technical side of Cyber Security. My main areas of expertise are Reverse Engineering, Infrastructure Security and Web Application Security.

Next to my work I am active as an Independent Hacker. I assist my customers in their journey to increase their security posture. I do this through advice, seminars and security assessments. I toot on the fediverse as @credmp@fosstodon.org.

I used to organize the Dutch meetup for Hack The Box, for which I was the ambassador in The Netherlands from 2020 to 2024. Each month, on the 3rd Wednesday, members of the Dutch cyber security community got together and shared presentations, demos and discussion on wide ranging topics.

Find my longer form writings in the Writing Category.

The views on this site are my own.

Enhance testability with selmer

This is my first article in a series called Rock Solid Software. In it I explore different dimensions of software that does not simply break. You can write good software in any programming language, although some are more suited to a disciplined practice then others, Clojure is definitely in the relaxed space of discipline here. Today I am exploring the use of Selmer templates in Clojure. If you have explored Biff at all you will know that all the UI logic works by sending Hiccup through a handler, which will turn into HTML through rum (specifically the wrap-render-rum middleware). If you provide a vector as a result for an endpoint, it will be converted to HTML. ...

October 8, 2024 - 4 min Arjen Wiersma

Choose your tools

I ❤️ to build software. I sadly do not have a lot of time next to my daily work to spend on my side projects, so I have to be disciplined in where I invest time. I wish I could spend endless amounts of time on exploring new technologies, but sadly I simply do not have that time. In writing this is sometimes referred to as “to kill your darlings”. Sir Arthur Quiller-Couch wrote in his 1916 book On the Art of Writing: “If you here require a practical rule of me, I will present you with this: ‘Whenever you feel an impulse to perpetrate a piece of exceptionally fine writing, obey it—whole-heartedly—and delete it before sending your manuscript to press. Murder your darlings.’” ...

September 30, 2024 - 2 min Arjen Wiersma

Bronnen beheren met Zotero [NL]

Je hebt tijd gereserveerd om te gaan studeren en je volgt een ritueel om goed in jouw “Deep Work” modus te komen, dat studeren gaat echt goed lukken! Tijdens de colleges en in de lesmaterialen vind je allerlei links naar papers, websites, YouTube videos en haal je veel informatie uit boeken. Al deze bronnen zijn zeer waardevol en bij de eindopdracht zul je veel van deze bronnen weer moeten gebruiken om argumenten te onderbouwen of juist iets te ontkrachten. Hoe ga je dan om met die bronnen zonder dat je gek wordt van allerlei documentjes? ...

September 3, 2024 - 3 min Arjen Wiersma

"Deep Work" voor het studeren [NL]

In mijn vorige artikel heb ik uitgelegd hoe je tijd kunt vinden om te studeren, de vraag is echter, is alle tijd hetzelfde? Het simpele antwoord is “nee”. Maar waarom niet, zul je vragen, en daarmee komen we op het onderwerp van dit artikel. Cal Newport heeft een fantastisch boek geschreven, “Deep Work: Rules for Focused Success in a Distracted World”. In dit boek onderzoekt hij hoe je gefocust werkt en wat er voor nodig is om gefocust te blijven [1]. In het boek identificeert hij 2 soorten werk; “Deep Work” en “Shallow Work”. Deze concepten hebben voor mij de aanpak van mijn dagelijkse werk zelfs veranderd, maar dat is een verhaal voor een andere keer. ...

August 21, 2024 - 6 min Arjen Wiersma

Finding time to study

This is an English article, there is also a Dutch version. So, you’ve decided to start studying? Maybe you want to earn your Bachelor or Master’s degree, or perhaps you’re aiming for that highly technical certificate. It’s great that you’re taking this step, but once you begin, you’ll quickly need to answer the question of where you’ll find the time. Time is our most valuable, non-renewable resource. Studying requires time – and not just a little – so you naturally want to use it well. Most programs expect you to invest between 12 and 24 hours per week to keep up, and that’s quite a bit! If you’re not currently studying, try thinking about which days and times you could free up that time. Will you eat out less or exercise less? Get up early on weekends or stay up late? ...

July 15, 2024 - 5 min Arjen Wiersma

Tijd vinden om te studeren [Dutch article]

This is a Dutch artcile, there is also an English version. Dus, jij hebt besloten om te gaan studeren? Misschien wil je jouw HBO- of Masterdiploma halen, of juist dat ene supertechnische certificaat bemachtigen. Het is geweldig dat je deze stap gaat zetten, maar zodra je begint, zul je vrij snel de vraag moeten beantwoorden waar je de tijd vandaan haalt. Tijd is onze meest waardevolle, niet-hernieuwbare bron. Studeren vergt tijd – en niet zo’n klein beetje ook – dus wil je het natuurlijk goed doen. De meeste studies verwachten dat je wekelijks ergens tussen de 12 en 24 uur investeert om bij te blijven, en dat is flink wat! Als je nog niet studeert, probeer dan eens na te denken over welke dagen en momenten je die tijd kunt vrijmaken. Ga je minder uit eten of juist minder sporten? Vroeg opstaan in het weekend, of juist extra laat naar bed? ...

July 15, 2024 - 6 min Arjen Wiersma

Master of Puppets^HScience!

So, on Thursday I defended my thesis in front of the graduation committee, and passed! This means that the work I have been doing for the last year comes to an end. From now on there are not long nights and weekends working on my thesis anymore. Back in 2021 I started my journey of achieving a Master’s degree, first with a connecting program and then with the 2 year Master program. Even though I have been in computer science in some form for the last 30 years I still found it to be quite a learning experience. ...

June 24, 2024 - 1 min Arjen Wiersma

Resigning as Hack The Box Ambassador

So, today I have some news. I will be resigning as Ambassador for Hack The Box after our in-person meetup in June (2024). This means that I will be stepping down from organizing the monthly virtual and quarterly in-person Hack The Box meetups. Let me explain how I got to this decision. The beginning So, in 2019, I started out building a cyber security curriculum for NOVI Hogeschool. I had the ability to greenfield the courses and create something that is of value to students. In this curriculum I started using Hack The Box for exercises and training next to the regular classwork. ...

May 28, 2024 - 5 min Arjen Wiersma

The cyber cafe podcast

Last week I was a guest on the Cyber Cafe podcast by rootsec. It was a fun discussion on education and the current xz backdoor story. It is in the Dutch language. It is available on youtube and included below:

April 9, 2024 - 1 min Arjen Wiersma

Microsoft Teams (v2) on Linux

This post is just a small note for those of you who also run Microsoft Teams on Linux through their browser and now receive a note “your browser does not meet the requirements for the new Teams”. It turns out that the client is looking at the user-agent string to determine which browsers it accepts, and which not. So, if you have the message, install an user-agent switcher and select a common browser on a common OS (from the MS perspective) and you will suddenly meet the requirements. ...

April 1, 2024 - 1 min Arjen Wiersma