Senior Penetration Tester

We are looking for a Senior Penetration Tester with CHECK to join our growing team. You will play a critical role in delivering high‑quality penetration testing engagements across infrastructure, cloud, web, and mobile applications for a diverse range of clients, including software, fintech, manufacturing, engineering, legal, and public sector organisations.

This is a hands‑on role where your expertise will help identify and remediate security weaknesses, while contributing to the development of our methodologies and mentoring junior testers. If you’re passionate about offensive security and want to work on varied, challenging projects in a supportive environment, we’d love to hear from you.

• CHECK Team Member (CTM) status
• Current UK Security Clearance
• At least 2+ years of penetration testing experience
• Strong experience with web application and network penetration testing methodologies
• In‑depth knowledge of operating systems (Linux, Windows, Active Directory)
• Familiarity with cloud environments and ability to perform cloud security reviews
• Proficiency with tools such as Burp Suite Pro, Nmap, Nessus, and Kali Linux
• Knowledge of scripting languages (Python, Shell, etc.)

• CHECK Team Lead (CTL) status (Infrastructure or Applications)
• Relevant certifications (OSCP, Cyber Scheme)
• Experience with Hack the Box or Capture the Flag simulations

• Recognition that matters: A discretionary annual performance bonus that rewards your impact and contribution to our success
• Flexibility built in:
  Flexible working arrangements and summer hours
• Financial security: A highly competitive pension scheme with generous employer contributions, private healthcare, and life assurance
• Health & wellbeing:
  Employee Assistance Programme, mental health support, cycle‑to‑work scheme, and regular social events
• Time to recharge: 35 days holiday, enhanced maternity pay, and family‑first policies
• Learning never stops:
  From courses to certifications, we’ll invest in your development
• Community & culture:
  Opportunities to volunteer, give back, and be part of initiatives that make Instil truly inclusive and connected