IT Systems Administrator - Cyber Security

We're looking for a senior IT Systems Administrator to join a major infrastructure-focused Cyber Security programme within a high-profile, 24x7 critical operational environment. This is a hands-on technical lead role, you'll be the primary bridge between the Cyber Security project team and IT Operations, driving security-hardened infrastructure change at scale.

You'll design, build, and maintain complex Microsoft-stack environments with a strong emphasis on security posture, resilience, and regulatory compliance, while mentoring junior engineers and keeping a complex estate healthy day to day.

What you'll be doing

• Acting as technical lead on cyber security infrastructure initiatives across a live 24x7 environment
• Designing and implementing best-practice infrastructure with a focus on security hardening, scalability, and resilience
• Managing vulnerability and security patch lifecycles
• Owning HA/DR strategies for critical applications
• Producing audit-ready documentation for internal and external review
• Monitoring infrastructure and security performance against SLAs
• Escalation point for complex technical issues from L1/L2 support
• Mentoring and developing first and second line engineers

• 5+ years senior experience with Microsoft technologies in large enterprise environments
• Expert-level Windows Server 2019/2022/2025 - implementation and administration
• Deep knowledge of Active Directory and Group Policy
• Strong understanding of network protocols, backup principles, and Windows 11
• Certified: CompTIA Security+, Microsoft 365/Azure security certifications (eg SC-300, MS-500)
• MCSA, MCP and/or CCNA (or equivalent experience)
• Proven ITIL process discipline and audit documentation experience

Right to work

Candidates must hold unrestricted right to work in the Republic of Ireland. This includes Irish and EU/EEA citizens, and holders of Stamp 4 or Stamp 5. We are unable to consider applications requiring employment permit sponsorship, including those currently on a Stamp 1/Critical Skills Employment Permit tied to another employer.

Apply now with your up to date CV. All suitable candidates will be contacted directly. This role requires candidates to be available to work on-site in Dublin and eligible to work in Ireland.