Job Title: Senior Network Security Engineer Duration: 1 year (on‑site first 3 months, then hybrid) Workload: Full time hours Setup: Freelance (Daily rate / Limited Company / Umbrella / Sole Trader) Location: Brussels HQ The client is seeking a Senior Network Security Engineer to strengthen a 24/7 operational network team managing IT and OT environments across multiple European sites. Key Responsibilities: Support, secure and operate complex network infrastructures across IT and OT environments. Execute and prepare network changes with high diligence in mission‑critical environments. Deploy and maintain network, firewall, cloud and wireless systems. Provide operational support to teams across Belgium and wider Europe. Participate in connectivity projects: new data centre setup, cloud integration, WAN modernisation and network security enhancements. Must‑Have Skills: Strong firewall expertise (Checkpoint required). Deep knowledge of routing/switching (OSPF, ISIS, MST). Experience with Cisco wireless, Cisco ACI, SD‑WAN, ASR/ISR/Catalyst/Nexus. Cloud experience (Azure). Automation experience with Python and/or Ansible. Monitoring/NAC/Syslog knowledge (Zabbix, Elastic, ISE). TACACS/RADIUS experience. Fluent English and either Dutch or French. Nice‑to‑Have: Juniper experience. Experience supporting both IT and OT network stacks. Willingness to join standby rotation (1 week in 4).