Senior Penetration Tester

JR United Kingdom; London; On-site; GBP 60,000 - 90,000; Full time

Job summary

A cyber consultancy specializing in penetration testing seeks a Senior Penetration Tester. This role involves leading complex assessments for diverse clients, including tech scale-ups and critical infrastructure providers. Candidates should have significant experience in penetration testing and relevant certifications, and be eager to work with an elite team of security specialists.

Qualifications

• Proven experience in penetration testing and red teaming (internal, external, app, cloud, etc.).
• Strong understanding of attacker TTPs and detection evasion.
• Familiarity with frameworks such as OWASP, MITRE ATT&CK, and NIST.

Responsibilities

• Lead and execute complex penetration tests and adversary simulations.
• Deliver red team engagements aligned with frameworks like TIBER, CBEST, and MITRE ATT&CK.
• Create detailed, client-facing technical and executive reports.

Skills

Penetration Testing

Red Teaming

Technical Documentation

Continuous Learning

Education

Certifications such as OSCP, CRTO, OSEP, or CREST CRT

Tools

C2 Frameworks

Cobalt Strike

PoshC2

Sliver

Job description

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Opus are looking for an experienced Penetration Tester to join our client, a cyber consultancy specialising exclusively in penetration testing and red teaming, delivering high-impact, adversary-simulated engagements for clients ranging from agile tech scale-ups to critical infrastructure providers. As a Senior Penetration Tester, you’ll play a central role in executing and shaping these engagements—across infrastructure, web, cloud, and bespoke environments—while also leading goal-based assessments and full-scale red team operations.

This is a hands-on, client-facing position suited to someone who thrives in technically demanding scenarios and wants to work alongside a small, elite team of offensive security specialists.

Key Responsibilities

• Lead and execute complex penetration tests and adversary simulations
• Deliver red team engagements aligned with frameworks like TIBER, CBEST, and MITRE ATT&CK
• Develop custom tooling and exploits where required
• Create detailed, client-facing technical and executive reports
• Mentor junior testers and contribute to internal R&D
• Stay sharp: engage in continuous learning and threat landscape analysis

About You

• Proven experience in penetration testing and red teaming (internal, external, app, cloud, etc.)
• Strong understanding of attacker TTPs and detection evasion
• Familiarity with frameworks such as OWASP, MITRE ATT&CK, and NIST
• Experience with C2 frameworks (e.g., Cobalt Strike, PoshC2, Sliver)
• Certifications such as OSCP, CRTO, OSEP, or CREST CRT preferred (but not required)