Penetration testing companies in the United Kingdom

CREST and CHECK-accredited European managed services provider delivering penetration testing with deep infrastructure and cloud hosting expertise.

The only organisation worldwide with a full suite of CREST accreditations. 250+ cybersecurity specialists operating in 55+ countries across pen testing, red teaming, and incident response.

Global cybersecurity consultancy with CREST, CHECK, and CBEST accreditation, renowned for deep technical research and penetration testing services.

London-based cybersecurity provider, now part of Kroll, delivering CREST-accredited penetration testing, managed detection and response, and incident response with a 550-strong cyber team.

Global Big Four professional services firm delivering CREST, CHECK, and CBEST-accredited penetration testing and red teaming services from London, serving the UK's largest enterprises and regulated organisations.

Fast-growing CREST and CHECK-accredited UK cybersecurity consultancy with deep expertise in critical national infrastructure sectors.

CREST and CHECK-accredited UK penetration testing and managed security provider formed in 2026 from Pentest People, Bulletproof, and Target Defense, with CREST STAR/TLPT-FS capability and the GuardNest vulnerability management platform.

UK compliance and cybersecurity consultancy, formerly IT Governance, offering CREST and NCSC CHECK penetration testing alongside governance, risk and compliance services.

Subscription-based offensive cybersecurity firm delivering continuous cyber attack services with CREST STAR and CBEST accreditations from its London headquarters.

Cardiff-based CREST and CHECK-accredited cyber security company delivering penetration testing, red teaming, and OT security assessments as part of the Chess Group.

Global enterprise cybersecurity consultancy founded in 1999 in Oxford, holding rare CREST STAR-FS accreditation and delivering penetration testing, red and purple teaming, and PCI QSA services across five international offices.

CREST-accredited, platform-driven penetration testing vendor in Bristol offering AI-augmented testing with rapid self-service booking for over 400 global customers.

The UK's largest independent security testing firm, renowned for IoT/OT research, CBEST red teaming, and CHECK/CREST-accredited penetration testing across all sectors.

London-based cybersecurity firm offering unlimited, fixed-price penetration testing and red teaming services with ISO 27001 certification and a unique subscription model.

CREST-accredited UK cyber security and data protection consultancy offering penetration testing, ISO consultancy, and managed SOC services from offices across the UK and Ireland.

CHECK and CREST-accredited Birmingham-based cyber security consultancy with over 15 years of experience delivering penetration testing, red teaming, and OT security assessments for government and private sector clients.

CREST-accredited Birmingham-based cyber security consultancy delivering penetration testing, social engineering assessments, and Cyber Essentials certification for public and private sector clients.

Full-service London-based cybersecurity consultancy with CREST, CHECK, and NCSC accreditations delivering offensive testing, managed detection, and strategic advisory services.

Elite UK offensive security consultancy specialising in CBEST/STAR/TIBER red teaming, advanced adversary simulation, and CREST-accredited penetration testing for FTSE 100 clients.

CREST-certified and PCI QSA penetration testing consultancy in London, delivering offensive security and compliance services across 25+ countries with research-driven expertise.

Award-winning Cheltenham-based cybersecurity consultancy with NCSC CHECK Green Light status and CREST approval, specialising in defence, government, and critical national infrastructure security.

Manchester-based independent cybersecurity consultancy with over 20 years of experience delivering CREST and CHECK-accredited penetration testing, red teaming, and compliance certification services.

UK offensive security consultancy delivering CREST-accredited penetration testing, adversary simulation and CBEST, TIBER-EU and TBEST threat-led testing, mainly for financial services and other large organisations.

Award-winning CREST-certified managed cyber security and IT support provider with offices in Bristol, London, and Manchester, specialising in penetration testing and Microsoft security technologies.

Edinburgh-based CREST-accredited IT and cybersecurity firm. Pen testing for Scottish public sector, financial services, and commercial clients.

CREST and CHECK-accredited UK penetration testing consultancy with CBEST approval, specialising in infrastructure, application, and simulated attack assessments across the public and private sectors.

Boutique UK penetration testing consultancy in Milton Keynes specialising in manual, expert-led security assessments across web applications, APIs, cloud, and mobile platforms.

Israeli-headquartered global cybersecurity consultancy with a UK presence, specialising in penetration testing and TIBER-EU red team exercises for Fortune 500 companies.

CREST-accredited North East England penetration testing specialist founded in 2019, offering accessible and transparent security testing with free retests and a strong focus on social engineering.

CREST-accredited UK penetration testing consultancy based in Shropshire, delivering web application, API, infrastructure, cloud, mobile, and AI/LLM testing. A small specialist team, with a retest included in every engagement.

CREST-accredited Manchester-based cyber security firm delivering penetration testing, managed security services, and compliance consultancy across the UK, Europe, and the USA.

Forefront IT Security Services presents itself as a virtual cyber security team for organisations in the United Kingdom.

Revelion provides an autonomous AI pentester that simulates attacks to validate exploitability across estates.

Soken is a Web3 services firm based in London.

CodeWall builds autonomous attack agents that test enterprise security from the outside.