Linux/Coms/Security Systems Administrator We are looking for a Senior Systems Administrator with extensive experience in Linux environments (especially Debian), virtualization, networking, and security, along with solid knowledge of Microsoft 365\. We seek a candidate for whom computing, security, communications, and Linux are not just a job, but a true passion and hobby. The selected individual will join a highly specialized team within a Spanish cybersecurity company. **Responsibilities in Linux environments (Debian and FreeBSD):** * Advanced system administration: installation, configuration, maintenance, optimization, and hardening. * Automation through scripting (Bash, Perl) and configuration management tools. * Performance analysis, resource optimization, and resolution of complex incidents. * Virtualization management using KVM, QEMU, and Proxmox VE environments. * Integration with internal services and cloud solutions. * File system administration (XFS, Ext4, ZFS), SystemD, boot processes, and high-availability environments. * Vulnerability management, continuous patching, and internal security audits. * Logging systems administration, IP security services, and filtering policies. * Operation of critical services such as SSH, Apache, and Postfix. * Advanced hardware diagnostics and deep understanding of server architectures. * Network, router, and firewall administration: * Management of routers and firewalls (pf, nftables, iptables, VyOS, MikroTik or similar). * Configuration and monitoring of LAN/WAN networks, VPNs, QoS, VLANs, and advanced routing. * Monitoring, OSI troubleshooting, and traffic analysis. * Implementation of network security best practices and perimeter hardening. **Responsibilities in Microsoft environments:** * Advanced administration of Microsoft 365\. * Automation and management using PowerShell. **Candidate Requirements:** * Genuine passion for computing, Linux, security, communications, and hardware. * Specialized technical education in Computer Science or equivalent. * Minimum of 5 years of experience managing Linux systems in demanding environments. * Experience in high-availability, virtualization, and security environments. * Advanced level of written and spoken English. * Professional relationship skills with enterprise-level clients. * Autonomy in solving complex problems and ability to work in a team. * Self-learning capability and a teaching attitude toward the rest of the team. * Practical knowledge of intrusion testing in Linux environments. * Experience with analysis and exploitation tools (Nmap, OpenVAS/Nessus, Metasploit, Burp Suite, or similar). * Ability to identify vulnerabilities, assess risks, prepare reports, and propose corrective measures. **Typical Job Tasks:** * Comprehensive administration of systems, virtualization, networks, hardware, and communications. * Design, validation, and implementation of new technical solutions. * Propose new ideas and improvements, taking full responsibility for their design, testing, implementation, and maintenance. * Conduct security tests, vulnerability analysis, and verification of system protection status. * Perform internal penetration tests in controlled environments. * Comprehensive management of backups and contingency plans. * Continuous improvement of internal procedures and security standards. * Participation in certification processes (ISO, ENS, etc.). * Advanced technical support to end clients. **We Offer:** * Permanent contract in a Spanish company specialized in cybersecurity. * Stable technical environment with complex projects and real challenges. * A solid and transparent work environment, free of internal conflicts, where everyone pulls in the same direction. Linux, M365,Microsoft 365, PowerShell,Bash, Perl