Penetration testing is about real attack paths, not a stunt. In the UK it sits as a steady engineering routine alongside DevSecOps, cloud workloads, and regulation. The goal is simple to say: surface issues before release, prove impact, close gaps fast, keep the team’s cadence. Not a shiny report – resilience tomorrow. Yes, sometimes it feels dull, but it works.
The outlook is clear: more continuous checks, focus on APIs and SaaS, sensible automation, AI for triage, with people making the calls. Choose a partner with care: sound method and transparency, accreditations such as CREST, re-testing, pipeline integration, careful data handling. This article reviews the best penetration testing companies in the United Kingdom based on public sources and market visibility – so you can compare approaches and pick one that fits your way of working without the drama.
1. A-Listware
We build and secure software, and we don’t treat those as separate worlds. Security testing sits inside the delivery rhythm, so pen tests land at the right time and actually help teams ship safer code. We run penetration testing for organizations in the United Kingdom – web, mobile, APIs, networks, and cloud – using real attack paths and reproducible steps, then work through fixes and retests without drama.
We’re a UK company with a permanent presence in East Sussex, and we list penetration testing under both Cybersecurity Services and Testing & QA. That means you can bring us in for a focused security engagement or fold us into a broader release cycle. Tooling is the usual mix you’d expect for serious work – Burp Suite, Nessus, Metasploit, Nmap, Wireshark – with manual verification where it matters.
When a project calls for formal checks, we align testing with compliance work. Our team delivers assessments and audits, PCI DSS and HIPAA readiness, and a Prevent-Detect-Respond operating model that includes penetration testing and stress testing when needed. In short – actionable findings, clear scope, and steady follow-through for UK customers.
Key Highlights:
- UK-registered company with a UK office and direct phone line for local engagements
- Penetration testing offered under both Cybersecurity Services and Testing & QA for flexible engagement models
- Operational model supports compliance initiatives including PCI DSS and HIPAA alongside technical testing
- Practical toolset in daily use – Burp Suite, Nessus, Metasploit, Nmap, Wireshark – with manual verification where needed
Services:
- Web application penetration testing for user flows, auth, and business logic
- API penetration testing for REST and GraphQL endpoints with schema-aware checks
- Network and infrastructure penetration testing for internal and perimeter assets
- Cloud security attack simulation and configuration hardening across AWS, Azure, and GCP
- Mobile application penetration testing with static and dynamic analysis
- Security code review for critical modules and high-risk changes
- Vulnerability scanning and ongoing security readiness advisory
- Compliance assessments and audit support for PCI DSS and HIPAA
- DDoS and stress testing scenarios to validate resilience under load
Contact Information:
- Website: a-listware.com
- Email: info@a-listware.com
- Facebook: www.facebook.com/alistware
- LinkedIn: www.linkedin.com/company/a-listware
- Address: St. Leonards-On-Sea, TN37 7TA, UK
- Phone Number: +44 (0)142 439 01 40
2. Testhouse
Testhouse is a quality engineering provider with a broad security practice that treats offensive testing as part of routine assurance, not a one off stunt. Pentest work spans applications and networks, from targeted probes against critical paths to broader reviews of exposed surfaces and access controls. Engagements often combine manual attack simulation with scanner-driven sweeps, then re-test to verify fixes and close the loop.
The team also bakes in security checks across delivery pipelines via DevSecOps, so weak spots surface earlier. Sector pages and case studies show penetration testing used alongside code review and performance work to keep systems steady under real pressure. Documentation in public listings further confirms penetration testing offered as a defined service within non-functional testing catalogs.
Highlights:
- Security testing sits inside mature QA workflows, not as an isolated task
- Use of penetration testing in live projects and documented case studies
- DevSecOps materials reference dedicated pentest activities and governance
Core offerings:
- Application penetration testing across web and mobile with re-test cycles
- Network and wireless assessments aligned to delivery pipelines
- Security code review paired with exploit verification to confirm impact
- Performance and security hardening for regulated environments where load and access control intersect
Get in touch:
- Website: www.testhouse.net
- Facebook: www.facebook.com/testhouseuk
- Twitter: x.com/testhouseuk
- LinkedIn: www.linkedin.com/company/testhouse
- Instagram: www.instagram.com/testhouse_
- Address: Level 18, 40 Bank Street, Canary Wharf, London E14 5NR, United Kingdom
- Phone: +44 20 8555 5577
3. Andersen
Andersen positions penetration testing as a structured, standards-led exercise rather than ad hoc ethical hacking. Service pages outline testing across web apps, mobile, APIs, IoT and internal or external networks, with options for red teaming where social vectors and physical paths are in scope. The practice cites OWASP, PTES, NIST and PCI guidance, with specific GDPR/PII assessments when personal data flows are central. Certifications shown include OSCP, CEH, GIAC and CREST, signaling alignment with common industry badges.
On delivery, Andersen combines manual exploitation with tooling, maps assets, scopes with customers, and documents remediation steps, then schedules re-testing to validate outcomes. Lead time claims and portfolio notes indicate a repeatable model rather than bespoke-only work. The catalog sits next to SOC and broader security management services, so penetration testing can plug into monitoring or incident response when needed.
Strengths:
- Coverage across web, mobile, APIs, IoT and network layers in one catalog
- Methods anchored to OWASP, PTES, NIST and PCI references
- Availability of red teaming for realistic attack simulation beyond pure app tests
- Visible certifications including OSCP, CEH, GIAC and CREST
Services include:
- Web application penetration testing with reporting and re-test cycles
- Mobile application assessments using static, dynamic and server-side checks
- API security testing for auth, input handling, rate limits and error management
- Network penetration testing and asset mapping, with options for SOC tie-in
Contact info:
- Website: andersenlab.com
- Email: vn@andersenlab.com
- Facebook: www.facebook.com/AndersenSoftwareDev
- Twitter: x.com/AndersenLabs
- LinkedIn: www.linkedin.com/company/andersen lab
- Instagram: www.instagram.com/andersen.global
- Address: 30 St Mary’s Axe, London, EC3A 8BF, UK
- Phone: +44 207 048 6755
4. Itransition
Itransition frames security work as a continuum: consulting, assessment, testing and managed improvements. Within that track, penetration testing sits next to vulnerability assessment and code review, giving customers a clear path from findings to fixes. The practice describes white-, grey- and black-box modes, mapped to OWASP and PTES methods, with activity staged from reconnaissance to exploitation and follow-up analysis. Output includes severity-ranked vulnerabilities and a remediation plan that feeds back into development cycles.
Beyond application layers, service notes reference infrastructure protection, network monitoring, cloud security and compliance support, so pentest results can be folded into broader security posture changes. Where teams need ongoing help, managed security and on-demand consulting are available, keeping the same methodology but extending it over time.
In practical terms, this means a test can start as a focused probe on a single app, then expand to networks or cloud components if evidence suggests lateral exposure. The write-up of steps and cooperative scoping process makes it clear the aim is repeatable improvement, not just a report. That balance of offensive testing with policy and monitoring gives stakeholders evidence and a path to action.
Standout qualities:
- Explicit white-, grey- and black-box penetration testing guided by OWASP and PTES
- Vulnerability assessment and secure code review offered alongside exploitation work
- Clear, staged process from reconnaissance to remediation planning
- Options to extend into cloud security, monitoring and compliance support
Practice areas:
- Application penetration testing with methodical evidence and severity ranking
- Network and infrastructure testing with follow-up hardening steps
- Vulnerability scanning plus manual verification to reduce noise
- Secure code review and advisory to convert findings into durable fixes
Reach out via:
- Website: www.itransition.com
- Email: info@itransition.com
- Facebook: www.facebook.com/Itransition
- Twitter: x.com/Itransition
- LinkedIn: www.linkedin.com/company/itransition
- Address: London 3rd floor, 5 8 Dysart St., EC2A 2BX
- Phone: +44 203 687 2281
5. Prolifics Testing
Prolifics Testing treats offensive security as a routine part of quality engineering, not a once-a-year checkbox. The practice runs focused attacks against web and mobile apps, plus external and internal networks, mixing human-led techniques with scanner-driven sweeps to uncover issues that slip through everyday checks. Findings don’t sit in a report and gather dust – re-tests confirm fixes and close the loop. Secure coding and pipeline checks are part of the toolkit, with static analysis woven into delivery so weak spots surface early. Vulnerability assessments complement deeper exploit work, giving teams a quick read on exposure before diving into full scenarios. It’s pragmatic, steady, and built to fit real release cycles, not slow them down.
Strengths:
- Penetration testing positioned inside a broader security testing catalog, not isolated activity
- Use of manual attack simulation blended with automated sweeps for coverage
- Code scanning and DevSecOps practices used to surface risks earlier in delivery
- Quick vulnerability audits available when a fast read on risk is needed
What they offer:
- Web application penetration testing with follow-up verification
- Mobile app security assessments alongside functional testing streams
- External and internal network penetration testing cycles
- Static code analysis and pipeline hardening with Fortify
- Vulnerability assessment with clear remediation guidance
Contact:
- Website: www.prolifics-testing.com
- E mail: info@prolifics testing.com
- Twitter: x.com/prolificstesting
- LinkedIn: www.linkedin.com/company/prolificstesting
- Address: 3 Penta Court Station Road Borehamwood, UK WD6 1SL
- Phone: +44 (0) 20 8905 2761
6. nFocus
nFocus approaches pen testing as repeatable security work that fits the release cadence. The team combines state-of-the-art scanning and exploitation tooling with human oversight, so applications and infrastructure get checked the same way every time and not only before big launches. Automation handles the routine, while testers focus on the tricky paths and authentication flows that scanners miss. Reports prioritise issues, which helps teams fix what matters first.
Beyond the day-to-day tests, the company publishes guidance on web application attack simulation and the role of automated checks between manual exercises. That viewpoint is simple enough – simulate real attackers, keep coverage high between formal engagements, and fold findings back into Agile and DevOps routines. The aim is consistent security evidence rather than one-off stunts.
Why people choose nFocus:
- Repeatable automated checks that complement hands-on exercises
- Coverage across web apps and underlying infrastructure in one offering
- Published guidance that explains method and limits of automation
Security services include:
- Web application penetration testing with authenticated user journeys considered
- Infrastructure and network penetration testing alongside app work
- Automated security scans scheduled per release to maintain coverage
- Advisory on embedding security testing into Agile and DevOps models
Contact:
- Website: www.nfocus.co.uk
- E-mail: info@nfocus.co.uk
- Facebook: www.facebook.com/nfocusltd
- Twitter: x.com/nfocus_ltd
- LinkedIn: www.linkedin.com/company/nfocus-ltd
- Instagram: www.instagram.com/nfocustesting
- Address: E-Innovation Centre, Shifnal Road Priorslee, Telford, Shropshire TF2 9FT
- Phone: +44 370 242 6235
7. TestingXperts
TestingXperts presents penetration testing as a structured service with clear coverage across applications, infrastructure, and cloud. The practice highlights AI-assisted techniques to widen discovery and reduce false positives, while keeping human-led exploitation at the core. Service pages break out testing types for web, mobile, desktop, wireless, and cloud, with language grounded in common frameworks and attack classes. It reads like a catalog you can plug into an existing program without disrupting it.
Mobile applications get special attention. Assessments target app code and the connected backend, mapping issues like insecure storage, weak auth, and data leakage before those slip into production. The guidance sticks to practical threats rather than buzzwords, which helps when scoping a first engagement.
For teams who want a bigger picture, blogs and explainers outline the purpose of penetration testing, typical attack paths, and how results feed compliance and risk reduction. That material supports scoping and stakeholder alignment, then the service catalog supplies the testers and the method.
What makes this practice stand out:
- AI-assisted techniques used to enhance discovery and cut noise
- Catalog covers apps, infrastructure, wireless, and cloud in distinct workstreams
- Guides and explainers available for scoping and stakeholder buy-in
- Attention to mobile security across code and backend services
Coverage areas:
- Web application penetration testing aligned to OWASP attack classes
- Infrastructure and network penetration testing with risk-based focus
- Mobile application penetration testing including iOS and Android specifics
- Cloud environment assessments for misconfiguration and access exposure
- Wireless network security testing to prevent unauthorised access
Get in touch:
- Website: www.testingxperts.com
- E-mail: info@testingxperts.com
- Facebook: www.facebook.com/testingxperts
- Twitter: x.com/TestingXperts
- LinkedIn: www.linkedin.com/company/testingxperts
- Address: 3rd Floor, Belmont, Belmont Road, Uxbridge, UB8 1HE, UK
- Phone: +44 203 743 3008
8. DeviQA
DeviQA runs penetration testing as a hands-on security exercise that lets real attack paths surface before bad actors do. Work spans web apps, APIs, networks, and mobile, with testers combining manual exploitation and disciplined tooling to expose weaknesses that scanners alone often miss. Findings arrive with remediation steps, then re-tests confirm fixes so issues do not quietly return. Social engineering simulations sit alongside technical probes to check human controls, not just code. Pipeline and static checks round things out, so risks show up earlier in delivery rather than at the end. The overall feel is practical – repeatable method, clear evidence, and closure rather than a report that gathers dust.
Why they’re worth a look:
- App, API, network, and mobile coverage described as first-class service lines
- Manual exploitation blended with automation to widen discovery and depth
- Re-testing offered to validate remediation and close findings properly
- Security know-how embedded into delivery via static and pipeline checks
Services include:
- Web application penetration testing with exploit verification and retest
- API security assessments targeting auth, input handling, and error paths
- Network penetration testing against routers, firewalls, and internal segments
- Mobile application assessments plus backend review for data exposure
- Social engineering exercises to measure phishing and process resilience
Reach out:
- Website: www.deviqa.com
- E-mail: info@deviqa.com
- Facebook: www.facebook.com/deviQASolutions
- LinkedIn: www.linkedin.com/company/deviqa
- Address: London, 9 Brighton Terrace
- Phone: +1 805 491 9331
9. KiwiQA
KiwiQA frames penetration testing as a structured program rather than a one-off ethical hacking sprint. Service notes call out threat-intel-led scoping, red team simulations, and specialist lanes for wireless, IoT, and ICS, with actionable guidance attached to each engagement. Reporting focuses on impact and mitigation, not just CVE lists, and supports re-tests so fixes are proven. The public material also dives into best practices and reporting essentials, which helps teams align before testing starts.
Security pages reference broader assurance alongside offensive work – vulnerability scanning, cloud checks, and routine automation that keeps coverage warm between formal exercises. Blogs expand on web application security and mobile considerations, keeping the conversation grounded in day-to-day risks rather than buzzwords. The result is a catalog that suits teams who want repeatable cycles with room for depth when signals demand it.
Standout qualities:
- Threat-intelligence approach with options for red team activity and social vectors
- Coverage that extends to wireless, IoT, and ICS where needed
- Guidance on reporting quality and what good evidence looks like
What they offer:
- Application penetration testing with impact-driven reporting and re-test
- Infrastructure and wireless assessments with automation to retain coverage
- IoT and ICS penetration engagements when operational systems are in play
- Cloud security checks and vulnerability scanning as ongoing guardrails
Contact info:
- Website: kiwiqa.co.uk
- E-mail: sales@kiwiqa.com
- Facebook: www.facebook.com/kiwiqaservicesptyltd
- Twitter: x.com/KQPSL
- LinkedIn: www.linkedin.com/company/kiwiqa-services
- Address: Vista Business Centre 50 Salisbury Rd Hounslow TW4 6JQ United Kingdom
- Phone: +61 472 869 800
10. Zoonou
Zoonou treats offensive security as a dedicated craft with accreditation to match. The practice is a CREST member, and service pages place web and mobile application penetration testing at the center of the catalog. Testers tailor scope to compliance and risk goals, then provide ranked findings and pragmatic fixes. The tone is steady and methodical – useful for product teams that want assurance without drama.
Coverage is wider than a single test cycle. Vulnerability scanning complements manual work for periodic or on-demand checks, while cloud configuration reviews catch missteps that create unnecessary exposure. Articles explain how manual and automated approaches fit together, which helps set expectations before work begins.
Quality signals show up in governance too. Materials reference ISO 9001 and ISO 27001, plus Cyber Essentials Plus, alongside team certifications like CSTP and CAST. That mix suggests disciplined delivery backed by recognised security standards. Penetration testing then becomes part of a consistent assurance rhythm rather than a single gate.
What they focus on:
- CREST member status with a focus on web and mobile applications
- Combination of manual pen testing with periodic vulnerability scanning
- Cloud configuration reviews available to reduce misconfiguration risk
Services include:
- Web application penetration testing with risk-based prioritisation
- Mobile application penetration testing delivered by in-house specialists
- Vulnerability scanning to maintain coverage between formal tests
- Cloud configuration assessment to harden identity, access, and storage paths
Get in touch:
- Website: zoonou.com
- E-mail: info@zoonou.com
- LinkedIn: www.linkedin.com/company/zoonou
- Instagram: www.instagram.com/zoonou
- Address: Suite 1, The Workshop 10 12 St Leonards Road Eastbourne, East Sussex BN21 3UH
- Phone: +44 (0) 1323 433 700
11. 4M Testing
4M Testing treats offensive checks as part of a broader security program rather than a one off fire drill. The application penetration testing page outlines a hands-on method focused on examining defenses from inside the application environment, with clear steps from reconnaissance to exploit and evidence collection. A companion security testing page sets out a simple flow – scope, execute, deliver results – which makes the work predictable for product teams. Where deeper insight is needed, source code review looks for hidden flaws and verifies that key controls are actually implemented. Together, these pieces form a practical path from findings to fixes without derailing delivery.
Why people choose them:
- Application penetration testing documented with a clear methodology
- Process described from scoping through testing to results handover
- Source code review offered to uncover design weaknesses and control gaps
- Security assurance sits alongside other test services for steady coverage
Core offerings:
- Web application penetration tests with evidence based reports
- Defined scope and result delivery as part of the testing lifecycle
- Source code review to validate critical security controls
- Broader quality checks referenced through functional and non functional tracks
Contact:
- Website: 4m-testing.co.uk
- E-mail: info@4m-testing.co.uk
- Address: City West Business Park Building 3, #Office 102, Leeds – LS12 6LN, UK
- Phone: +44 113 543 2979
12. Qualitest
Qualitest positions penetration testing inside a larger cyber assurance toolkit. The security solutions catalog lists attack simulation across web, API, mobile and network, plus pipeline friendly checks with static, dynamic and interactive analysis so security lives alongside delivery. Sector specific and bespoke options are available when unusual stacks or domains are in play. The team also publishes perspectives on using machine learning to enhance discovery and reduce noise during engagements.
Guidance materials explain how to keep security close to Agile teams rather than parking it at the end, and case studies show security and data compliance mapped into real product work. The overall approach reads as structured, standards aware, and built to plug into existing programs without drama. Evidence and remediation come first, then re-checks where needed.
Why they stand out:
- Penetration testing covered for web, API, mobile and network in the solutions catalog
- Security by design with SAST, DAST and IAST integrated into build flows
- Practical guidance on collaborating with delivery teams through podcasts and explainers
- Case studies outlining security and GDPR alignment for complex products
Service scope:
- Web and API penetration tests with realistic attack simulation and actionable reporting
- Mobile application security assessments that extend to backend interactions
- Network and infrastructure testing aligned to established practices
- Consulting for threat modeling, DevSecOps adoption and risk impact assessments
Contact:
- Website: www.qualitestgroup.com
- Facebook: www.facebook.com/Qualitestgroup
- Twitter: x.com/QualiTest
- LinkedIn: www.linkedin.com/company/qualitest
- Instagram: www.instagram.com/lifeataqualitest
- Address: London, UK, Level 2, Equitable House 47 King William Street, EC4R 9AF
13. TestDel
TestDel lists penetration testing in its core service set with a straightforward goal – check whether unauthorized access to corporate or personal data is possible and close the gaps that make it so. Public pages reference security testing as a dedicated line of work and describe web exposure checks that span front and back end, plus network level testing when perimeter and internal paths are in scope. The emphasis is practical and report driven, with findings framed so fixes can be planned.
Broader testing notes confirm coverage across web, mobile and desktop, supported by a mix of manual and automated techniques. An in-house lab setup is described for safe, scalable execution, which helps when tests need controlled environments or repeatable runs. That makes it easier to fold security checks into ongoing delivery without constant context switching.
Technology pages round out the picture with stack familiarity useful for scoping and test design. Put together, the catalog supports routine application reviews, network probes, and targeted assessments where risk signals point. The intent is simple enough – find issues that matter, document impact, and guide remediation.
What makes them unique:
- Penetration testing explicitly listed in the primary offerings
- Network level and web layer checks described for end to end coverage
- Dedicated lab environment outlined for safe and repeatable testing
What they do:
- Web application penetration tests with vulnerability discovery from front to back end
- Network penetration testing for perimeter and internal exposure
- Mobile and desktop security assessments tailored to platform specifics
- Security testing program setup and ongoing checks via the security testing service
Get in touch:
- Website: testdel.com
- Email: team@testdel.com
- Facebook: www.facebook.com/testdel/about
- Twitter: x.com/testdelgroup
- LinkedIn: www.linkedin.com/company/testdelgroup
- Instagram: www.instagram.com/testdelgroup
- Address: 21 Woodfield Road, Hounslow, Middlesex TW4 6LL, UK
- Phone: +44 207 993 60 54
14. NCC Group
NCC Group runs penetration testing as a disciplined practice that blends realistic attack simulation with methodical assessment across applications and networks. Engagements cover web and mobile builds with optional code review, plus staged exercises like red and purple team operations that mirror how real attackers move. Infrastructure checks dig into internal and external exposure, configuration hygiene, and device build reviews so weak points are caught before release.
For teams that need continuous assurance, network testing can run in always-on mode to surface issues between formal windows. Results map cleanly to remediation and common frameworks, so fixes land where risk is highest rather than getting stuck in reports. It’s practical security work that fits product cadence and compliance needs without excess ceremony.
Why they’re worth checking out:
- Application and mobile assessments available, including structured mobile reviews and code analysis when needed
- Network testing covers internal and external paths with an approach that evolves alongside attacker techniques
- Attack simulation options span red and purple teaming for realistic defense measurement
- Reporting and guidance align to recognized standards and regulatory frameworks
Their focus areas:
- Web and mobile application penetration testing with optional secure code review
- Network penetration testing with configuration and build reviews for devices and systems
- Red team and purple team exercises to validate detection and response in practice
- Cloud and architecture assurance where service hardening is required
Contact info:
- Website: www.nccgroup.com
- LinkedIn: www.linkedin.com/company/ncc-group
- Address: XYZ Building 2 Hardman Boulevard Spinningfields Manchester M3 3AQ
- Phone: +44 (0) 161 209 5200
15. Pentest People
Pentest People treats offensive testing as an ongoing program, not a once-and-done audit. Core services span web applications, APIs, networks and mobile, with consultants following a manual-first methodology and using automation to widen coverage without drowning teams in noise. Findings flow into SecurePortal, a live platform that tracks vulnerabilities, evidence and retest progress so work doesn’t vanish into PDFs. Accreditation and public guidance sit alongside the services, which makes scoping easier for stakeholders who want predictable outcomes and clear method.
The catalog includes options for CREST-aligned assessments and specialist variants such as OVS for web, plus published explainers on infrastructure testing so expectations are set before execution. Blog material also covers when manual testing is essential, where automation helps, and how to blend both into release rhythms. It reads as a steady, standards-aware setup with practical delivery touches like re-testing built in.
What makes this practice distinct:
- SecurePortal provides a live view of findings, remediation status and re-tests
- CREST recognition referenced for penetration testing and incident response capability
- Coverage across web, API, mobile and network layers with clear service pages
Core offerings:
- Web application penetration testing with authenticated journeys and proof-of-concept evidence
- Network penetration testing for internal and external exposure with realistic attack simulation
- CREST OVS web assessments where source-level assurance is required by policy
- Consulting and enablement through methodology guides and structured re-testing cycles
Reach out:
- Website: www.pentestpeople.com
- E-mail: info@pentestpeople.com
- Facebook: www.facebook.com/pentestpeople
- Twitter: x.com/pentestpeople
- LinkedIn: www.linkedin.com/company/pentestpeople
- Address: 20 Grosvenor Place, London, United Kingdom, SW1X 7HN
- Phone: 0330 311 0990
Conclusion
Pen testing is not a one-off stunt but a practical way to validate security. It reveals real attack paths, proves controls, and gives teams facts, not hunches. The trick is cadence and tight alignment with releases. Picking a provider matters. Look for method and coverage, experience in your stack, clear reports with evidence and prioritisation. Re-test is a must. Integration with DevSecOps, careful data handling, and explicit UK legal context should be present. CREST and similar badges help, yet judgement comes first.
Practice matters too. Start with crisp goals and a narrow scope, then grow. Agree test windows, white/grey/black box mode, and communication lines. Ask for a remediation plan and progress metrics. Keep cycles short. Capture lessons early – security improves without the drama.
