Incident response firms in the United Kingdom

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.

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.

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.

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.

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

Provides cybersecurity protection and risk management for maritime vessels, offshore facilities and ports.

Cyber advisory and managed security services, including managed extended detection and response, cloud security, digital identity and threat intelligence, from a global professional services network.

Cybersecurity consulting and managed services covering security transformation, incident response, data protection and privacy, identity and privileged access, and operational technology security.

Littlefish provides managed IT services, cyber security, digital solutions, and data and AI services to organisations.