Job Title: IT Security Tester
Location: Aylesbury
Job Type: Full-Time
Experience Required: 4-5 Years
Reports to: Managing Director
Industry: Information Technology / Cybersecurity
Job Summary:
We are seeking a skilled IT Security Tester with 4 to 5 years of experience to join our cybersecurity team. The Security Tester will be responsible for identifying and addressing security vulnerabilities across applications, systems, and networks. The role requires a hands-on professional with expertise in Security testing, vulnerability assessments, and secure coding practices, working closely with developers, engineers, and other stakeholders to ensure the overall security posture of the organization.
-Key Responsibilities:
• Define and maintain test strategy, test plans, and test approach (functional, non-functional, regression, UAT) aligned to project delivery and business outcomes.
• Elicit and review requirements/user stories, ensuring they are testable, clear, and mapped to acceptance criteria and quality gates.
• Design, document, and execute manual test cases covering positive/negative scenarios, edge cases, and data validation checks.
• Develop and maintain automated test scripts (where applicable) to improve test coverage, speed, and repeatability across releases.
• Perform system, integration, and end-to-end testing across applications, APIs, databases, and third-party integrations.
• Conduct non-functional testing including performance, reliability, accessibility, usability, and basic security testing in line with organisational standards.
• Manage test environments and test data, ensuring readiness, integrity, and compliance with data protection requirements.
• Log, triage, and track defects in a defect management tool; provide clear reproduction steps, severity/priority assessment, and evidence.
• Work collaboratively with developers and engineers to support root cause analysis, retesting, and verification of fixes.
• Maintain traceability from requirements → test cases → results → defects, ensuring full auditability and coverage reporting.
• Produce and present test execution reports (test metrics, pass/fail rates, defect trends, release readiness) to stakeholders.
• Support release and change processes, including go/no-go decisions, regression sign-off, and post-release quality monitoring.
• Contribute to continuous improvement by refining testing standards, templates, and best practices, and mentoring others where needed.
• Ensure quality practices align with SDLC/Agile/DevOps delivery models, participating in ceremonies (refinement, sprint planning, reviews).
• Promote a culture of quality ownership, risk-based testing, and proactive issue prevention across teams.
- Technical Skills:
Certifications :
Testing / QA (core)
• ISTQB Certified Tester – Foundation Level (CTFL)
• ISTQB Agile Tester (Foundation Extension)
• ISTQB Test Automation Engineer (Advanced) (if you do automation heavily)
• ISEB Foundation in Software Testing (UK legacy, still recognised in some places)
Security testing / AppSec (to include security testing)
• Certified Ethical Hacker (CEH) (broad, recognisable; not purely testing-focused)
• CompTIA Security (good baseline security knowledge for testers)
- Soft Skills:
- Strong analytical skills and attention to detail.
- Excellent verbal and written communication skills.
- Ability to work independently and as part of a cross-functional team.
- Strong problem-solving and decision-making skills in a high-pressure environment.
Preferred Qualifications:
- Experience with cloud security testing (AWS, Azure, GCP).
- Knowledge of DevSecOps practices and tools (e.g., Jenkins, Git, Docker, Kubernetes).
- Familiarity with security frameworks and regulatory requirements (e.g., PCI-DSS, ISO 27001, GDPR).
Benefits
days of holiday, plus the option to buy or sell up to five additional days.
- A competitive salary and comprehensive benefits.
- Continuous learning and development opportunities.
Join Kelltron and contribute to shaping a secure digital future, leveraging our advanced products and services to make a significant impact in the field of cybersecurity.
To Apply:
Please send your resume and cover letter to with the subject line "Security Tester Application – [Your Name]."