Marlon Leerkotte's CV

• Email: marlon@leerkotte.net
• Location: Enschede, NL
• LinkedIn: marlonleerkotte

Experience

GroupSecure B.V., Security Consultant

Enschede, NL

Jan 2025 – present

1 year 2 months

• Providing on-site and remote consultancy for customers, with a focus on cross- and inter-vendor firewall migrations.

• Executing security scans for customers

• Implementing customer firewalls (Sophos XG, Palo Alto NGFW and Panorama)

• Managing customer firewalls (Palo Alto NGFW, Sophos XG)

• Managing endpoint security (Sophos Endpoint Security)

• Managing customer switches & wireless (Meraki)

• Supporting customers (phone and email)

• Architecting and supporting internal IT operations

GroupSecure B.V., Security Engineer

Enschede, NL

Oct 2020 – Dec 2024

4 years 3 months

• Providing on-site and remote consultancy for customers, with a focus on cross- and inter-vendor firewall migrations.

• Executing security scans for customers

• Implementing customer firewalls (Sophos XG, Palo Alto NGFW and Panorama)

• Managing customer firewalls (Palo Alto NGFW, Sophos XG)

• Managing endpoint security (Sophos Endpoint Security)

• Managing customer switches & wireless (Meraki)

• Supporting customers (phone and email)

• Architecting and supporting internal IT operations

Contec B.V., IT Security Support Engineer

Enschede, NL

Oct 2020 – present

5 years 5 months

• Managing internal IT (Proxmox, Linux)

• Managing FileCap SaaS infrastructure (AWS, Terraform)

• DevOps for FileCap (GitLab CI)

• Release engineering FileCap Appliance

• Implementing a K8S based SaaS platform

• Implementing a K8S based monitoring platform with edge deployments

• Supporting customers (phone and email)

Contec B.V., IT Security Trainee

Enschede, NL

Feb 2015 – Oct 2020

5 years 9 months

• Release engineering FileCap appliance.

• Supporting internal IT-operations.

• Implementing DevOps principles.

• Setting-up monitoring systems

Politie Oost-Nederland, intern

Zwolle, NL

Sept 2019 – Jan 2020

5 months

Implementing a new secure infrastructure for the Young Professional Track.

Contec B.V., intern

Enschede, NL

Jan 2016 – June 2016

6 months

Contec B.V., intern

Enschede, NL

Aug 2014 – Jan 2015

6 months

Projects

Manufacturing company triple firewall migration

Sept 2025 – Dec 2025

Replaced three Palo Alto Networks NGFW clusters with minimal impact on production.

Healthcare organisation core firewall migration (Hillstone>Palo Alto)

Mar 2025

Migrated core firewall from Hillstone to Palo Alto Networks NGFW.

• Healthcare organisation with 1000+ employees

• 1500+ firewall rules

• Python scripted migration

Education

Hogeschool Windesheim, Infrastructure Design and Security

BSc

Zwolle, NL

2016 – 2020

Bachelor’s specialization focused on networking, systems, and infrastructure security. The programme covered routing and switching (CCNA-level), Windows Server and Linux administration, and core security concepts such as firewalls, network segmentation, and monitoring. Most courses were hands-on and project-based. During group projects within the specialization, complete infrastructures were designed and built, including network topology, server environments, and basic security controls. The degree provided a solid technical foundation for roles in infrastructure, networking, and security engineering.

• Completed 207/240 credits towards degree

• Routing and switching at CCNA level, including network design and troubleshooting

• Windows Server and Linux administration in mixed environments

• Core network and infrastructure security concepts (firewalls, segmentation, monitoring)

• Virtualization and cloud fundamentals used in infrastructure setups

• Discipline-specific group projects designing and building complete infrastructures

ROC van Twente, Network administration

MBO4

Hengelo, NL

2013 – 2016

MBO-4 programme focused on the basics of network and system administration. The curriculum covered routing and switching fundamentals, Windows and Linux administration, and user support in small to medium-sized environments. The programme was largely practical, with lab work and projects involving setting up networks, managing servers and workstations, and troubleshooting common infrastructure issues. It provided a solid foundation for junior infrastructure roles and further study in ICT.

• Basics of routing, switching, and TCP/IP networking

• Windows and Linux system and workstation administration

• Setting up and maintaining small to medium-sized networks

• Troubleshooting network, system, and user issues

• Practical lab work and project-based assignments

Skills

Networking & Security: Firewall design and migration, cross- and inter-vendor migrations, Palo Alto NGFW (Panorama), Sophos (XGS, XG, UTM), network segmentation and hardening, VLANs, BGP, OSPF, NAT, VPNs

Systems & Infrastructure: Linux administration, Windows Server administration, virtualization (Proxmox, VMware), internal IT infrastructure design and operations

Cloud & Platform Engineering: AWS, Scaleway (SCW), Infrastructure as Code (Terraform), Kubernetes platform engineering, Kubernetes-based SaaS and monitoring platforms, edge deployments, CI/CD (GitLab CI), release engineering

Containers & Packaging: Docker, Podman, Buildah, container image build and release workflows

Monitoring & Operations: Zabbix, Grafana, ELK stack (basic usage), incident response, audit support and remediation

Automation & Tooling: Bash, Python, Git, GitLab workflows

Networking Platforms: Palo Alto Networks, Sophos, Meraki, UniFi

Professional Skills: Customer-facing consultancy, on-site and remote support, technical documentation, incident communication, audit collaboration, requirements analysis, working in small technical teams

Certifications: Sophos Firewall Technician, Sophos Firewall Engineer, Sophos Firewall Architect, Palo Alto Networks Accredited Systems Engineer (PSE/PSA)