Security Systems Architect

THE OPPORTUNITY

We are seeking a Security Systems Architect to define, design, and implement robust security solutions across server and network environments within a complex, high-assurance infrastructure. The role focuses on hardening systems, enforcing security requirements, and ensuring alignment with broader network architecture, alongside supporting proactive security validation activities such as penetration testing.

This position is well-suited to a senior security professional with strong experience in infrastructure security, system hardening, and secure architecture design, operating within regulated or mission-critical environments.

Key Responsibilities

• Define and implement server security requirements, including baseline configurations, hardening standards, and compliance controls
• Lead network device hardening activities (e.g. firewalls, routers, switches), ensuring alignment with security policies and best practices
• Develop and maintain secure system architectures, ensuring integration with wider infrastructure and enterprise network designs
• Manage and coordinate interfaces with network architecture teams, ensuring consistency across security and network domains
• Identify and mitigate security risks and vulnerabilities across systems and infrastructure components
• Support and contribute to penetration testing (pentesting) activities, including:
• preparation and scope definition
• remediation of findings
• validation of security controls
• Produce and maintain security design documentation, including architecture artefacts, standards, and procedures
• Ensure systems meet applicable security standards, compliance requirements, and accreditation needs
• Provide technical guidance to engineering and delivery teams on secure design and implementation
  
  

Essential Skills

• Strong understanding of system and network security architecture principles

Hands-on experience with server hardening (Linux/Windows) and secure configuration management

Experience in network security, including firewalls, routing, segmentation, and access control

Knowledge of security standards and frameworks (e.g. NIST, ISO 27001, CIS benchmarks)

Familiarity with penetration testing methodologies and vulnerability management processes

Ability to define and enforce security requirements and controls across infrastructure

Experience working with secure system integration and multi-domain environments

Strong analytical and problem-solving skills

Excellent stakeholder communication and documentation capability

Essential Expeirence

• Proven experience in a Security Architect, Security Engineer, or Systems Security role
• Experience designing and implementing secure infrastructure solutions in complex environments
• Demonstrated experience in system hardening and security configuration management
• Experience working with network architecture and infrastructure teams
• Involvement in security assurance activities, including vulnerability management and penetration testing support
• Experience producing security architecture documentation and technical standards
• Background in regulated, high-assurance, or mission-critical environments is highly desirable
  
  

With five strategic offices in Belfast, Chester, Farnborough, London and Oxford, we work in partnership with our customers UK-wide to deliver high-impact engineering solutions.

SII UK is a trusted Aerospace and Defence engineering partner, supporting the delivery of complex, mission-critical programmes while helping to shape the future of innovation across next-generation systems and technologies.

Our teams contribute daily to creating a fulfilling, stimulating and career development focused work environment.

True to our human-centred values, we are committed to making SII UK a Great Place To Work®, having been certified 5 years running.

Joining SII UK means being part of our collective goals, guided by our mission “Let’s Tech Together,” and helping to build a digital future that is sustainable, at the heart of an environment that values learning & collaboration.

Who are we?

With five strategic offices in Belfast, Chester, Farnborough, London and Oxford, we work in partnership with our customers UK-wide to deliver high-impact engineering solutions.

SII UK is a trusted Aerospace and Defence engineering partner, supporting the delivery of complex, mission-critical programmes while helping to shape the future of innovation across next-generation systems and technologies.

Our teams contribute daily to creating a fulfilling, stimulating and career development focused work environment.

True to our human-centred values, we are committed to making SII UK a Great Place To Work®, having been certified 5 years running.

Joining SII UK means being part of our collective goals, guided by our mission “Let’s Tech Together,” and helping to build a digital future that is sustainable, at the heart of an environment that values learning & collaboration.