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Secur!ty is everyone's concern...

but it's our bus!ness

g3rt is the company behind Gert Nelen, a network security specialist with more then 15 years of hands on experience in some of the most demanding networks and many other fields involving security.

We provide ICT consultancy services, focusing on everything related to network and system security.

Cyberthreats are real and we need to fend off attacks more often than we know. The challenge is to know in what to invest, where to invest it and how to make sure the investment keeps delivering at peak performance. A great many times organizations have all the reporting and prevention tools at the time of an attack on premise that - if configured correctly - could have prevented that same attack. By providing analysis skills and a specialized knowledge of security best practices on all levels of the field we would like to help companies maximize the defensive output of their security budgets.

presenting: Gert


Gert Nelen

ICT Security Specialist



+32 474 86 19 44



gert.nelen at 



August Van Doorslaerlaan 55

1860 Meise


Date of Birth:

July 15th, 1979

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Hello! I'm Gert


Having worked more then 20 years in  the domain of network infrastructure and security and more than 10 years working for and with intelligence services, I have a lot of experience to bring to the table. I have worked in very heterogenous environments with extreme security requirements, built networks compliant with NATO and EU standards and advised in several breach incidents. I have hands-on experience on a number of tools and platforms, among which Palo Alto, Fortinet, Juniper, Suricata, Cisco, WDATP, QRadar, TheHive,... I can work in and with a team and can communicate clearly.



ICT Security Specialist

g3rt bvba

I started my own firm knowing I have a specific specialist view because of the variety of interesting cases I have encountered over the years. I think g3rt is the logical next step for me to keep finding those challenges that keep life interesting.


A very diverse and complex network with high security requirements and a vast number of secured connections all over the world form a challenging playground. I could acquire experience in both blue and red team operations and succesfully worked with companies and agencies globally to try and make 'cyber' a little 'safer'. 

Network Security Engineer
Network-and systemadministrator


I got a great start in this challenging environment and started out writing firewalls, hardening unix servers, managing ids and building tunnels for this quickly growing secured network.



Post Academic Training

2021 Certified CCSP, Brucon 2021 Operational Threat Intelligence,2020 Certified CISSP, Brucon 2019 Full Stack Exploitation, Brucon 2018, Network Data Exfiltration Techniques-Post Exploitation, SANS SEC560 Network Penetration Testing and Ethical Hacking, SANS SEC660 Advanced Penetration Testing, Exploit Writing and Ethical Hacking, SANS SEC575 Mobile Device Security and Ethical Hacking, SANS SEC760 Advanced Exploit Development for Penetration Testers, Suricata Intrusion Detection Training, SANS SEC511 Continuous Monitoring and Security Operations, Ethical Hacking (tailormade) by John Cordier Academy, Fortinet Professional by Exclusive Networks, Fortinet Specialist by Fortinet, Juniper JNCP, VMWare ESXi 5.5 configure and install, Powershell, SANS FOR500 Windows Forensics Analysis, SANS FOR508 Advanced Digital Forensics, Incident Response and Threat Hunting, SANS FOR572 Advanced Network Forensics and Analysis, SANS SEC503 Intrusion Detection In-Depth. I regularly visit security-conventions/seminares (ICCS, ISS world, Black Hat, Brucon, ...) to keep me informed of the latest developments in the field.


Graduate applied computer science

Rega Instituut - Katholieke Hogeschool Leuven

Learned some of the basics in here. Interesting internship in java developement at Vlaams Parlement.

High School Diploma

Humaniora - Latin / Sciences

Languages, math, sciences, you have to learn the basics somewhere. I went to College van het Eucharistisch Hart in Essen (Belgium).


English - Dutch - French

Fortinet - experience with many of their products and advanced set-ups.

Advanced network architecture and engineering - from design to implementation.

Proficient with several scripting and programming languages (powershell, java, python, ...)

Red Team and Blue team skills

(Cyber)security specialty. Threat hunting, detection optimization, custom sandboxing,...

Network Defense

Having defended very complex and highly valued networks for a long time with quite some succes, I have acquired thorough knowledge of complex layer 2 and layer 3 networks and their different levels of defense. I also have hands-on configuration experience on many products (open source, fortinet, juniper, cisco, epicom, ...), beit firewalls, honeynets, ids, ips, central logging, SIEM, system hardening or sandboxing.

Incident Handling

Depending on the nature of the incident every breach benefits of 2 things most: thorough (but quick) analysis and decisive response. 

When an attack is discovered it needs to be handled rather then neglected. A team should be prepared for reacting when an attack occurs. They should know what to do and how to quickly limit the damage, without destroying the evidence.

Network analysis

Having worked with, connected and secured so many networks great and small to all different levels of protection gives me the ability to analyse the current protection, it's configuration and advise on possible investments, reconfigurations, changing your work(er) processes or other improvements to better protect your most valuable assets.

What can we do for you?
Training is key to security!

Train your IT-staff, train your suppliers, train your users (especially those), train yourself, train as many people as possible in 'the ways of security'. At any level, training pays off. Wether it be users not clicking on any link they see, firewall staff knowing to clean up their old routes, incident response teams knowing to dump the memory before taking down the infected host,...

I'm not a trainer and do not give lessons in the common sense of the word. I can however train smaller teams in the use and configuration of network security components or any other area of expertise I can help in.

No security without analysis!

Analysis should be the beginning of any network security project. Analyse the risks, analyse the cost (of non-investment), analyse the work processes, analyse the weak spots and look what you can do to defend those as well. Sometimes it is a good idea to have someone external to your organization look at the infrastructure and it's defenses and analyse if (and where) there is room for improvement. 

When requested I can help implement improvements myself, or connect you with the right people for your specific request.

After analysis, improvements!

After a detailed analysis, we can write different levels of reports, from very limited (list of vulnerabilities found), to extremely detailed, with POC data, suggested configuration changes, ...

In any case you 'll allways get a report with advise on the most easy ways you can patch the vulnerabilities found, along with an explanation of the impact the breach of this vulnerability would cause. This helps make decisions about the investment to protect against the vulnerability more educated.

Good configurations make all the difference

In many cases the firms targeted by cybercrime have all the security components and logging components available in their network they need to detect and prevent a breach, but simply lack the know-how of how to collect that data, wash it and act upon it. They often have devices seeing that traffic, but malconfigured to raise the alarm.

I can assist in configuring many sorts of networks, servers and security devices and understand the principles of network security like no other.

When all else failed....
When despite all your efforts to prevent the bad guys from entering your network and systems you get breached nevertheless, all hell breaks loose. You need to swiftly make critical decisions about how to manage the crisis and get on top of things. A good start is a trained incident response team, but they are generally only found in the larger companies. The second best thing is to get (your) experts together, analyze the situation and create a clear path towards the solution. I have some experience in this field and can help when needed. Discretion assured; pgp key available on this site.
Here you can check my availability

I'm just one man and I might not be available much during periods in which I am on a full-time contract on a project. Here I'll keep you posted on my current contract load and duration. Smaller assists or assesments might always be possible. For any information you can always contact me. 

Currently I am in a full-time contract until 31st of december 2024

I'm working for a big retailer in the operational security field. This is a long-term assignment. The current contract will end 30/06/2022

Values we hold high...

Discretion is one of the most important pillars, next to the trust relationship between security consultant and client. A clear and open communication between all levels involved and respect for each person's expertise are very important for a succesfull coöperation. I usually make my deadlines and am dedicated to the project I'm working on.

For secure mailcommunication you can download the public pgp key for gert.nelen at

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