applied security research

About Zolder

Welcome to Zolder! We started this company in March 2020. With 4 fellows, sharing a decent amount of experience as cybersecurity professionals, we have set course to build a great and indefinite working environment for hackers. Because that is who we are, and we believe the availability of hacking skills will be paramount for succesful digital societies.

From Zolder we provide help through security services and software to companies.

Currently we are working on a platform to assess and monitor cloud infrastructure like Microsoft 365. Our goal is to provide SMB with a security governance tool that will match their needs. It will allow us to help a large set of customers with insights we get from our own security research efforts.

Furthermore today we provide time-based services on-demand, like security testing services (e.g. penetration testing), give lectures and presentations as well as training. Let us know what you need, we can probably help out. Contact us through social media or contactform.

Currently, as we are doing fundamental work in setting up our business, we focus on our local business. Therefore most content you will find here will be in Dutch. However, we do post and speak in English every now and then.

Please follow us on social media to stay up to date.


In a dynamic society – in which the digitization of the world around us is increasingly being implemented through robotization, virtual reality, and IoT (Internet of Things) – the social need for a knowledge safety net to carry out that digitization in a controlled fashion is growing. Especially now that the developments and uncertainties related to the COVID-19 crisis show that more and more organizations are storing their data in the cloud, and video conferencing has taken off. Applied digital security research is crucial to create protection for organizations that want to be well prepared for all the technological possibilities the future offers.

Analytical thinking of professional hackers, cyber researchers, software developers, and security consultants is necessary to find solutions to security issues that may not yet exist or that do not present a direct problem. The specialisms required to perform this applied security research have now been brought together under one roof: Zolder.

The real ‘diehard’ cybersecurity experts have learned the tricks of the trade in their attic room. That attic room mentality stands for technical craftsmanship and love for cybersecurity. Zolder was founded as a company based on a deep-rooted passion for all developments related to security in the digital domain. The four founders (Rik van Duijn, Wesley Neelen, Theo Snelleman, and Erik Remmelzwaal), who have met each other as direct colleagues at DearBytes/KPN Security, can always be woken up for a security challenge.

The Zolder team mainly wants to create a company that forms a foundation for security work. Together, Rik, Theo, Erik, and Wesley have over thirty years of work experience in various domains of cybersecurity research. The four have specific hacking, malware, reverse engineering, data analysis, and IT management skills. Customers can rely on their in-depth digital knowledge: from the basics of electrical engineering to networking, operating systems, and applications, incident response in case of virus outbreaks and strategic development of both security hardware and software.

The main goal of the four at Zolder is to be able to conduct autonomous and pragmatically applied security research for parties who need it. Because a substantial part of the Dutch business community is already transforming and implementing digitization processes, it is extremely important from a social perspective that security professionals think about how we can safely adopt the digital technology of the future. Zolder responds to this need by using all jointly accumulated knowledge and experience in the development of new technology. This offers digital protection for all technological possibilities and challenges of the future. It is especially important to invest as much time as possible in research and in this way to convert all knowledge and capacity into value for customers and society in general. Ultimately, the Zolder mentality is characterized by being big and strong, precisely by staying small and operating smartly.


Zolder.App LIVE Presentations

Erik Remmelzwaal - 11 jan 2021
During #CES2021 we will host a daily LIVE event in Microsoft Teams – OPEN FOR ALL, so also available for non-CES-visitors and non-Teams-users. Monday – Tuesday – Wednesday from 17:00 – 17:30 CET / 11:00 – 11:30 AM EST. The events will be hosted by Erik Remmelzwaal in English. The sessions will be opened for […] Lees verder

#CES2021 - We Are Ready!

Erik Remmelzwaal - 06 jan 2021
We are very excited to be part of the #CES2021NL mission! Meet us at CES (Januari 11-14) in our online booth 10609 and see how we solve global challenges with NLTech. Erik Remmelzwaal, Co-Founder & CEO Yes I indeed think we are ready for CES. At this virtual event we will showcase Zolder.App. I am […] Lees verder

Azure App Consent Policies

Rik van Duijn - 11 nov 2020
OAuth consent phishing has been on the rise for a while now. Unsurprisingly, Microsoft has gradually introduced measures to protect from this type of attack. Latest: Risk-Based Step-Up Consent. Lees verder

Honeytokens using Azure Keyvaults

Rik van Duijn - 15 okt 2020
In 2017 Wesley and I gave a presentation at SHA2017 about honey/pot/tokens. We actually planned on building a fully fledged platform. But never came further then the POC phase of that project. This week we got a product demo from the guys at Thinkst, i’ve always loved this way of thinking: let the attacker come […] Lees verder

Risk of exposed home automation services

Wesley Neelen - 24 sep 2020
At home, I am automating many things for fun. Currently I am using Home Assistant, an incredibly powerful piece of software for automating your home. Regularly I am combining the home automation experiences with security. Home automation is often related to physical things such as changing lights, moving curtains, opening door locks or turning the […] Lees verder

Hacking the traffic light of the future

Wesley Neelen - 06 aug 2020
Nowadays we are connecting everything we can think of to the internet. Usually to make our lives easier or more comfortable. Some of the new upcoming innovations are related to making our traffic smart with the goal to improve safety, comfort and the traffic flow. We dived into this technology to analyze the inner workings and identify potential security risks. Lees verder

Detect lateral movement with Azure Sentinel

Wesley Neelen - 01 jul 2020
Lately we have been setting up a the production network for our Zolder.App service. The network consists of multiple segments separated by a firewall. As an addition we wanted to add monitoring features into the network. If an attacker is in our network, we would like to get a notification. Lees verder

Detecting BEC fraud using Azure Sentinel

Rik van Duijn - 17 jun 2020
Business Email Compromise (BEC) Fraud inflicts the most damage of all types of cybercrime, according to the FBI. How to detect such attacks using Azure Sentinel? Rik shares some actual possibilities. Lees verder

Phishing aftercare

Rik van Duijn - 26 mei 2020
This blog is part of our Office 365 attack & defense series. We also maintain a Github page where we share our Office 365 tools and queries. We often get sent phishing emails by family and friends. Not to phish us but because we ask family and friends to forward them to us. Sometimes they […] Lees verder

Inside a phishing panel

Wesley Neelen - 20 mei 2020
Dutch and Belgium citizens are receiving phishing attacks every day. But how does that exactly work? Lees verder

Office 365 - Exchange rules

Rik van Duijn - 13 mei 2020
This blog is part of our Office 365 attack & defense series. We also maintain a Github page where we share our Office 365 tools and queries. Exchange rules can be useful in managing the emails we receive on a daily basis. For example, it allows users to automatically respond or move specific emails to […] Lees verder

Office 365 - malicious applications

Wesley Neelen - 05 mei 2020
Wesley dives into the App Registrations feature of Microsoft Azure Active Directory. Finds ways to abuse it through delegate & application permissions and shares ideas howto protect from such abuse. Lees verder

Windows terminal profile fun

Rik van Duijn - 24 apr 2020
Rik plays around with the preview version of Windows Terminal to find manipulation options. Lees verder

Building a Zolder logo

Wesley Neelen - 22 apr 2020
Wesley writes about his most recent IoT project: building a Zolder logo with WS2812B ledstrips behind it, to give it some cool effects. Lees verder