Independent comparison
Best penetration testing companies in the UK
An evidence-based shortlist of UK penetration testing providers, ordered by the accreditations we could verify against public records — not by who paid. Every firm below holds recognised UK credentials and offers core network and web-application testing.
How this list is compiled
There is no single “best” pentest firm — the right provider depends on your scope, sector, and compliance drivers. So rather than invent a ranking, we order this list by the depth of accreditation we could independently verify from public records (CREST Marketplace, the NCSC CHECK list, and certification registers).
Ordering is never influenced by payment. Featured placements, when they exist, are always labelled and sit outside the editorial order. Use the filters in the full directory to narrow by service, accreditation, and size.
PenTesting.org is an independent editorial directory. We are not an accreditation body or association and are not affiliated with CREST, the NCSC, OWASP, PCI SSC, or ISO. Accreditations are reported from public sources, with the evidence linked on each listing.
53 companies
Claranet Cyber Security
Large (201–1000)
Cyber security division of Claranet providing CREST-accredited penetration testing, application testing and managed security services.
Pen Test Partners
Size not stated
UK consultancy offering CREST-accredited penetration testing across web, mobile, infrastructure and specialist areas such as maritime, automotive and aviation.
Cyberfort Limited
Large (201–1000)
UK cyber security group offering CREST-accredited penetration testing, incident response and secure hosting.
MDSec Consulting Ltd
Mid-size (51–200)
UK consultancy specialising in CREST-accredited penetration testing and financial-sector threat-led testing (CBEST, GBEST, TIBER-EU).
AmberWolf
Small (11–50)
UK offensive security firm offering CREST-accredited penetration testing and financial-sector threat-led testing (STAR-FS).
Avord Ltd
Small (11–50)
UK provider delivering CREST-accredited penetration testing through an online security-testing platform.
Closed Door Security Ltd
Small (11–50)
UK-based cyber security firm (with UAE and US offices) offering CREST-accredited penetration testing.
Cognisys Group Ltd
Mid-size (51–200)
UK cyber security firm offering CREST-accredited penetration testing including web and mobile application testing.
Cyberis Reply Ltd
Small (11–50)
UK consultancy (part of Reply) offering CREST-accredited penetration testing and financial-sector threat-led testing (STAR-FS).
D2 Network Associates Ltd
Small (11–50)
UK IT and cyber security firm offering CREST-accredited penetration testing and managed security services.
Dionach Ltd
Mid-size (51–200)
UK consultancy offering CREST-accredited penetration testing, incident response and information security auditing.
Intruder
Mid-size (51–200)
UK vulnerability-management and attack-surface monitoring platform with CREST-accredited vulnerability assessment and PTaaS offering.
IOActive Inc
Large (201–1000)
Research-led security firm with a UK CREST-accredited entity offering penetration testing and hardware/embedded security assessment.
JUMPSEC Ltd
Small (11–50)
UK cyber security consultancy offering CREST-accredited penetration testing, threat-led testing and managed detection services.
Orange Cyberdefense
Large (201–1000)
UK arm of the international Orange Cyberdefense group offering CREST-accredited penetration testing and managed security.
Prism Infosec Ltd
Cheltenham · Small (11–50)
Cheltenham-based consultancy offering CREST-accredited penetration testing and financial-sector threat-led testing (STAR-FS).
Rootshell Security Ltd
Mid-size (51–200)
UK firm providing CREST-accredited penetration testing alongside the Rootshell vulnerability-management platform.
Secarma Ltd
Small (11–50)
UK cyber security consultancy offering CREST-accredited penetration testing and vulnerability assessment.
SecQuest Information Security Ltd
Small (11–50)
UK information security consultancy providing CREST-accredited penetration testing and Cyber Essentials certification.
UK Cyber Defence Ltd
Cambridge · Small (11–50)
Cambridge-based cyber security firm offering CREST-accredited penetration testing and managed security services.
2-sec Consulting
London · Small (11–50)
London-based consultancy offering CREST-accredited penetration testing, incident response and PCI compliance.
4ARMED Ltd
Boutique (1–10)
UK penetration testing firm holding CREST accreditation, known for cloud and application security testing.
Bridewell
Large (201–1000)
UK cyber security consultancy offering CREST-accredited penetration testing, threat-led testing, managed detection and response.
Citation Cyber
Small (11–50)
UK cyber security provider offering CREST-accredited penetration testing and compliance services.
CNS Group
Large (201–1000)
UK cyber security provider (part of Six Degrees) offering CREST-accredited penetration testing and vulnerability assessment.
CovertSwarm
Mid-size (51–200)
UK offensive security firm offering CREST-accredited continuous red teaming and penetration testing on a subscription model.
CyberCrowd
Small (11–50)
UK information risk and cyber security provider offering CREST-accredited penetration testing.
Cyphere
Boutique (1–10)
UK penetration testing firm offering CREST-accredited infrastructure and web application testing and Cyber Essentials certification.
edgescan (BCC Risk Advisory Ltd)
Large (201–1000)
Ireland-based provider (serving the UK) delivering CREST-accredited penetration testing and continuous vulnerability management via a PTaaS platform.
Exosec Ltd
Boutique (1–10)
UK penetration testing firm holding CREST accreditation and Cyber Essentials Plus.
Fortbridge
Boutique (1–10)
UK boutique penetration testing firm holding CREST accreditation and Cyber Essentials Plus.
Leo CybSec
Boutique (1–10)
UK cyber security consultancy holding CREST accreditation for penetration testing.
NCC Group
Manchester · Enterprise (1000+)
UK-headquartered global cyber security firm providing CREST-accredited penetration testing, threat-led testing, incident response and threat intelligence.
ONSecurity Technology Limited
Mid-size (51–200)
UK provider delivering CREST-accredited penetration testing through a subscription-based online platform.
Pentest Cyber
Boutique (1–10)
UK penetration testing firm holding CREST accreditation and Cyber Essentials Plus.
ProCheckUp Ltd
Small (11–50)
Long-established UK consultancy offering CREST-accredited penetration testing, vulnerability assessment and incident response.
Reversec
Large (201–1000)
UK offensive security consultancy (formerly WithSecure Consulting) offering CREST-accredited penetration testing and threat-led testing (CBEST, GBEST, TIBER-EU).
Salus Digital Security Ltd (SalusCyber)
Cheltenham · Small (11–50)
Cheltenham-based cyber security firm offering CREST-accredited penetration testing.
The SecOps Group
Boutique (1–10)
UK security firm offering CREST-accredited penetration testing and security certification training.
Thomas Murray Cyber Limited
Small (11–50)
Cyber division of Thomas Murray offering CREST-accredited penetration testing and incident response.
Truststream Cybersecurity Limited
Large (201–1000)
UK cyber security firm (part of SysGroup) offering CREST-accredited penetration testing.
Arcanum Cyber
Mid-size (51–200)
UK cyber security consultancy offering CREST-accredited penetration testing and security consultancy.
Blackfoot UK Ltd
Small (11–50)
UK cyber security and data protection consultancy holding CREST accreditation for penetration testing.
Cynance Consulting Ltd
Boutique (1–10)
UK consultancy offering CREST-accredited penetration testing and security risk management.
Foregenix Ltd
Large (201–1000)
UK-headquartered global firm offering CREST-accredited penetration testing, digital forensics and PCI compliance services.
Illume
Boutique (1–10)
UK cyber security specialist offering CREST-accredited penetration testing, social engineering, cloud reviews and wireless auditing.
Laneden Ltd
Boutique (1–10)
UK boutique security firm holding CREST accreditation for penetration testing.
Liora Security Solutions Limited
Boutique (1–10)
UK security firm holding CREST accreditation for penetration testing.
Mobius Binary Limited
Small (11–50)
UK security firm holding CREST accreditation for penetration testing.
Pentest People
Leeds · Size not stated
Leeds-based consultancy delivering NCSC CHECK-assured penetration testing through its SecurePortal platform.
Ruptura InfoSecurity
Small (11–50)
UK penetration testing provider holding CREST accreditation for penetration testing services.
Secure Impact Ltd
Boutique (1–10)
UK penetration testing firm holding CREST accreditation.
Securious Limited
Exeter · Small (11–50)
Exeter-based cyber security firm holding CREST accreditation for penetration testing.
Frequently asked questions
- How do you decide which companies are "best"?
- We order firms by the accreditations we can verify against public records — CREST, NCSC CHECK, ISO 27001, and Cyber Essentials Plus — because those are the objective quality signals a buyer can check. We do not sell ranking positions, and we do not publish an opinion score for a firm we have not independently reviewed.
- What accreditation matters most for a UK penetration test?
- CREST accreditation is the most widely recognised mark of a competent UK testing provider, because member firms are assessed on methodology and quality assurance, and their testers hold individual certifications. If you are testing public-sector systems, look for NCSC CHECK status as well.
- Are these companies affiliated with PenTesting.org?
- No. We are an independent directory. We compile listings from public sources and are not affiliated with any of the firms listed, nor with CREST, the NCSC, or any accreditation body.
- How much does a penetration test cost?
- A typical UK penetration test ranges from a few thousand pounds for a focused web-application or external network test to tens of thousands for a large, multi-workstream engagement or red team. Cost is driven by scope, complexity, and the seniority of the testers.