Senior Penetration Tester

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

Job summary

A leading cyber consultancy is seeking an experienced Senior Penetration Tester to join their elite team. This hands-on role involves leading penetration tests and red team operations across various environments, requiring strong technical expertise and the ability to mentor junior team members. Candidates should possess proven experience in penetration testing with a solid understanding of attacker tactics, techniques, and procedures (TTPs).

Qualifications

• Experience in penetration testing and red teaming (internal, external, app, cloud).
• Strong understanding of frameworks like OWASP, MITRE ATT&CK, and NIST.
• Proven ability to deliver technical assessments and reports.

Responsibilities

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

Skills

Penetration testing

Red teaming

Attacker TTPs

Detection evasion

Education

OSCP

CRTO

OSEP

CREST CRT

Tools

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)