Cybersecurity companies in the United Kingdom

Darktrace provides AI-powered cybersecurity solutions that detect and respond to threats across networks, cloud, email, and AI systems.

Cybersecurity consulting division of global insurance leader Aon, uniquely combining penetration testing with cyber risk quantification and insurance expertise.

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 cybersecurity and compliance provider offering penetration testing, managed security services, and regulatory consultancy to over 2,000 customers from its Stevenage headquarters.

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.

CREST, CHECK, and CBEST accredited UK consultancy within Lloyd's Register, delivering premium penetration testing for government and critical infrastructure.

CREST and CHECK-accredited UK penetration testing firm with an SecurePortal platform and transparent pricing for mid-market organizations.

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.

Antare provides AI-powered body cameras and an evidence platform for frontline security.

Automiq is an automation strategy and transformation partner.

Bondgate IT is a managed service provider founded in 1998.

ISO/IEC 27001 certification audits and information security training from the UK national standards body, which also certifies quality, safety and medical devices.

UK security consultancy doing threat modelling, training and research for connected vehicles, IoT and mobile products.

Corero Network Security provides automatic DDoS protection for businesses and service providers.

CronLab provides web and WiFi filtering services.

CybaVerse provides a unified cyber security operations platform called CybaOps.

CybSafe provides an AI-powered platform that helps organisations measure and change security behaviours to reduce breaches.

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.

Egress provides cloud email security that uses adaptive controls to stop phishing and data loss.

Ethixbase360 sells third-party risk management software and due diligence services.

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

Fendr provides AI usage controls for businesses.

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

GTMaritime provides secure communication and cybersecurity software for maritime IT teams.

UK vehicle engineering and test centre offering threat modelling, CSMS support and security testing for vehicles.

IDScan provides identity document verification software to authenticate customers and prevent fraud.

Immersive Labs sells a platform called Immersive One that helps organisations show how ready they are for cyber threats.

Testing and certification group that helps vehicle makers and suppliers work towards ISO/SAE 21434 compliance.

Cyber security consulting covering strategy and governance, security transformation and cyber threat management, plus cyber managed services and cloud security from member firms.

Mimecast provides email security and human risk management services for organisations.

Netcraft detects, disrupts and takes down phishing, fraud and other cybercrime threats for brands.

Nethermind is a blockchain research, engineering and security company.

Notice Labs sells trust center software to software companies that face customer security reviews.

OSINT Industries provides open-source intelligence tools for online investigations.

Ossprey Security is a cybersecurity company that focuses on detecting malicious code in open source dependencies.

Outerlimit provides a security and authorization layer for agentic AI systems.

Red Sift provides email, domain and web security services to help organisations implement security protocols.

Report URI is a client-side security platform that monitors and controls what runs in users' browsers.

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

RoboShadow provides daily vulnerability scanning and automated remediation for internal and external networks.

UK automotive consultancy that runs vehicle penetration tests, threat assessments and anti-theft testing for carmakers.

SealGate provides a security gateway that governs how AI agents access company data.

Shufti provides identity verification, KYC, AML screening and fraud prevention software for businesses worldwide.

Silobreaker provides a software platform that gathers and analyses security and risk intelligence for organisations.

Soken is a Web3 services firm based in London.

Provides an AI security engineer that finds and fixes software risks using coding agents.

ValidSoft provides voice authentication and deepfake detection.

Vulert monitors open-source dependencies for vulnerabilities and license compliance without accessing source code.

Web Sheriff is an online rights protection agency founded in 2000.

42Crunch provides security governance for MCP servers and APIs used by AI agents.

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

HackRisk monitors external cyber risks for UK SMEs and provides a security score.

Intruder provides continuous vulnerability scanning and attack surface management for cloud and web assets.

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

Secvura reviews web and SaaS applications for security weaknesses and helps teams fix them.

System Force IT provides managed IT support, cyber security, and Microsoft 365 services to UK SMEs.