LLM / AI Penetration Testing2026-08-17T07:37:32+00:00

LLM / AI Penetration Testing

CodeShield delivers CREST-accredited AI and LLM penetration testing to organisations building artificial intelligence into their products across the UK.

Get a FREE penetration test quote today

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CREST accredited LLM / AI penetration testing

LLM / AI penetration testing services

CodeShield delivers CREST-accredited AI and LLM penetration testing to organisations building artificial intelligence into their products across the UK. The moment you connect a large language model to your data, your tools, and your users, you introduce a class of risk that traditional security testing was never designed to catch.

Prompt injection, data leakage, and models tricked into acting far beyond their remit are not theoretical. They are already being exploited in the wild. We test your AI systems the way a real adversary would, then give you clear, prioritised findings and practical guidance to make them safe. No hype, no fear-selling. Just a dedicated expert who works with you from scoping through to fixing every issue we find.

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What is AI and LLM penetration testing?

AI penetration testing is a specialised security assessment of the systems you build around artificial intelligence, most commonly applications powered by large language models such as GPT, Claude, Gemini, or your own fine-tuned and open-source models.

Unlike a traditional application test, which focuses on code and infrastructure, AI penetration testing targets the behaviour of the model itself and the ways it interacts with your data, your users, and the tools it can control. It asks a different set of questions. Can the model be manipulated into ignoring its instructions? Can it be coaxed into revealing sensitive data or another user’s information? Can untrusted content hijack it? Can it be pushed into taking actions it was never meant to take?

Our specialists combine established application security expertise with adversarial AI testing techniques, assessing your system against the OWASP Top 10 for LLM Applications and going beyond it, to give you a genuine picture of how your AI would hold up under attack.

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What our AI and LLM penetration testing covers

AI systems have an attack surface that spans the model, the application around it, the data it draws on, and the tools it can act upon. We test all of it.

  • Prompt injection: The defining vulnerability of LLM applications. We test both direct injection, where a user manipulates the model through crafted input, and indirect injection, where malicious instructions are hidden in content the model later processes, such as a document, web page, or email. This is where most serious AI compromises begin.

  • Jailbreaking and guardrail bypass: We probe the safety controls and system prompts meant to keep your model in line, testing how easily they can be overridden to produce prohibited output or unintended behaviour.

  • Sensitive data disclosure: We test whether your model can be led into revealing confidential information, including training data, system prompts, credentials, or the data of other users, a critical risk for any multi-tenant or data-connected application.

  • Insecure output handling: An LLM’s output is untrusted input to whatever consumes it. We test whether model responses can trigger downstream vulnerabilities such as cross-site scripting, SQL injection, or command execution in your wider application.

  • Excessive agency and agentic risks: As models gain the ability to call tools, access APIs, and take actions, the stakes rise sharply. We test AI agents for excessive permissions, unsafe tool use, and the risk of being manipulated into performing damaging actions on your behalf.

  • RAG and knowledge base security: For retrieval-augmented generation systems, we test the pipeline that feeds your model, assessing access controls, data poisoning risks, and whether users can reach information they shouldn’t through the model.

  • Model and API security: We test the infrastructure around your AI, including authentication, rate limiting, and the APIs that expose it, as well as risks such as model denial of service and model theft.

  • Supply chain and plugin security: We assess the third-party models, plugins, and components your system depends on, where a single insecure integration can undermine the whole application.

WHY TRUST CODESHIELD

Trusted & Independently verified.

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“We recently engaged CodeShield to carry out penetration testing for one of our clients, and the service was nothing short of excellent. Both Tom and Dan were extremely knowledgeable and professional throughout the process. Their clear communication and technical expertise made the entire experience smooth and efficient. We look forward to working with them again when the need arises and would highly recommend their services.”

Darren Walsh

“We’ve used a number of CREST assured pen testing companies over the last 10 years, however CodeShield have been the first to exceed my expectations. The team listened to what we wanted, added their own expertise and recommendations and then performed a bespoke test with meaningful, well set out results. The follow-up meetings between our dev team and the testers was well run and respectful. I highly recommend CodeShield and will be engaging them again for our future testing.”

Daren Martin

“We used CodeShield for a security and penetration testing audit for one of our clients. As well as being technically competent and very efficient in carrying out the audit, they were extremely communicative and collaborative throughout the whole process. The result is that we are now very well equipped for the big launch and rolling out the platform to Schools securely.”

Justin Coulston

Client’s we’ve worked with.

CREST-accredited mobile application penetration testing you can trust

When it comes to security testing, credentials matter, and AI security is a field where genuine expertise is in short supply. CodeShield is a CREST accredited penetration testing company, holding one of the most respected accreditations in the industry, and we bring that same rigour to emerging AI threats.

CREST accreditation isn’t a badge you buy. It’s independent proof that our methodologies, technical expertise, data handling, and quality processes have been rigorously assessed against internationally recognised standards. For you, it means the testing of your AI systems is carried out to a benchmark your clients, auditors, and stakeholders already know and trust.

Why CREST accreditation matters for your business

  • Independent assurance: your testing is validated against standards set and monitored by the industry’s leading not-for-profit accreditation body.
  • Procurement-ready: many enterprise customers and public sector frameworks require, or strongly prefer, a CREST accredited provider before they’ll engage.
  • Compliance confidence: CREST accredited testing supports frameworks like ISO 27001, SOC 2, and the emerging ISO 42001 AI standard, giving auditors the credible evidence they’re looking for.
  • Certified people, not just a certified company: our testers hold individual industry certifications from bodies including CREST and Offensive Security, so your project is always in expert hands.

When you choose CodeShield, you’re partnering with a trusted UK security consultancy that combines independent accreditation, technical excellence, and clear guidance to protect your business against real-world threats, including the newest ones.

AI penetration testing for organisations building with AI

AI penetration testing matters most to organisations embedding large language models into products, workflows, and customer experiences, especially those handling sensitive data or operating in regulated markets.

If you are deploying an AI chatbot, building an LLM feature into your software, or giving an AI agent access to your systems, AI penetration testing should be part of your security programme from day one.

Securing the AI features and copilots you’re building into your platform.
Protecting AI-driven tools that touch customer accounts and financial data under FCA expectations.
Securing AI systems that handle patient data and clinical information.
Testing AI used in underwriting, claims, and customer interaction.
Securing the chatbots and virtual assistants that now sit on the front line of your brand.
Safeguarding the confidential data flowing through AI-assisted research and document tools.
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Meet your compliance and governance requirements

AI governance is moving quickly, and independent security testing is fast becoming an expectation rather than a nice-to-have. Many organisations come to us to satisfy a framework, reassure an enterprise customer, or get ahead of regulation. We make that straightforward, and turn it into genuine security improvement.

Our AI and LLM penetration testing supports:

  • ISO 42001: independent testing to evidence the security controls within your AI management system, the first international standard dedicated to responsible AI.

  • OWASP Top 10 for LLM Applications: testing against the recognised benchmark for large language model security.

  • NIST AI Risk Management Framework: supporting a structured, evidence-based approach to AI risk.

  • EU AI Act: helping you demonstrate the risk management and robustness expectations placed on higher-risk AI systems.

  • ISO 27001, SOC 2 and GDPR: aligning your AI security with your wider information security and data protection obligations.

You’ll receive a clear, audit-ready report that maps findings to the standard you’re testing against, plus practical remediation advice to close the gaps, not just document them.

WHY CODESHIELD – 20+ YEARS EXPERIENCE

You work with the person doing the testing. Not a sales team.

At CodeShield, our UK penetration testing team brings 20+ years of combined expertise delivering practical, results-driven security solutions tailored to your business.

You work directly with a fully-qualified pen tester. You meet them before you pay, so you know who you’re working with.

  • Find & Fix Vulnerabilities: Uncover hidden threats with expert-led testing and gain true confidence in your security.
  • Simplify Compliance: Navigate ISO, PCI DSS, SOC 2 & DSPT with clear, actionable guidance, not just box-ticking.
  • Strengthen Your Defences:  Prioritise real risks and improve your security posture with insights from seasoned professionals.
  • Save Time & Reduce Complexity: We handle the technical details, letting you stay focused on your business.
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TRUSTED UK PENETRATION TESTERS

Contact CodeShield today to get a quote or work with us

At CodeShield, our UK penetration testing team brings 20+ years of combined expertise delivering practical, results-driven security solutions tailored to your business.

Get a FREE penetration test quote today

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What makes our AI penetration testing different

  • CREST accredited, independently assured: Choosing a CREST-accredited penetration testing company means your testing is carried out to internationally recognised standards, the assurance your clients, auditors, and stakeholders are looking for.

  • Genuine AI security expertise: AI security is a specialism, not an add-on. We combine established application security experience with adversarial AI techniques, so you get testers who understand both the model and the system it lives in.

  • Manual, adversarial testing, not just a scan: Automated tools barely scratch the surface of AI risk. Our specialists think like an attacker, crafting the creative, chained, context-aware attacks that scanners simply cannot replicate.

  • One dedicated expert, start to finish: No handoffs, no account-manager buffer. The specialist who scopes your test runs it and debriefs you personally.

  • Reports people actually act on: Prioritised by risk, written to be understood by technical teams and non-technical stakeholders alike, with clear remediation steps for every finding.

Our Values

Open Mindedness

We believe there’s no single solution to a security challenge. By staying open to new ideas and approaches, our teams find the best outcomes for every unique obstacle we face.

Honesty & Integrity

We believe there’s no single solution to a security challenge. By staying open to new ideas and approaches, our teams find the best outcomes for every unique obstacle we face.

Professionalism

We believe there’s no single solution to a security challenge. By staying open to new ideas and approaches, our teams find the best outcomes for every unique obstacle we face.

Collaboration

We believe there’s no single solution to a security challenge. By staying open to new ideas and approaches, our teams find the best outcomes for every unique obstacle we face.

What’s in your AI penetration testing report

The report is where a penetration test earns its value. A test is only as useful as the document that comes out of it, and ours are built to be read and acted on, not filed away. Every engagement ends with a clear, structured report that works for your technical team and your senior stakeholders alike.

  • Executive summary: A plain-English overview of what we tested, what we found, and what it means for your business, written so a non-technical reader can understand your AI risk position in a couple of minutes.

  • Risk-prioritised findings: Every vulnerability we identify, rated by severity and real-world impact, so you know exactly what to fix first. No noise, no padding, just the issues that matter, in the order they matter.

  • Technical detail and proof of concept: For each finding, a clear explanation of the vulnerability, proof-of-concept evidence showing how it could be exploited, and everything your team needs to reproduce and verify the issue.

  • Practical remediation advice: Actionable, specific guidance on how to fix each finding, from strengthening system prompts and input handling to tightening the permissions of your AI agents. This is the part clients tell us they value most.

  • Compliance mapping: Where relevant, findings are mapped to the standard you’re testing against, including ISO 42001 and the OWASP Top 10 for LLM Applications, so the report slots straight into your governance or certification process.

  • Debrief and support: The report isn’t the end of the conversation. We walk your team through the findings in a debrief session, answer their questions, and stay on hand as you work through remediation.

See a sample report

Want to see the quality of our reporting before you commit? Download an anonymised sample AI penetration testing report and see exactly what you’ll receive: the structure, the depth of detail, and the clarity of our remediation advice.

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Not sure which test you need?

Most people searching “pen test” aren’t sure yet, that’s normal. Pick the closest match, or talk it through directly with a tester. We can incorporate multiple testing types for a single project. We often do web app + network testing if a business wants to cover both.

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Web Application Pen Testing

Customer-facing apps, portals and API layers.

Great for SAAS businesses.

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Network Penetration Testing

Internal and external infrastructure, patch…

Great for network heavy businesses.

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Cloud Penetration Testing

AWS, Azure, GCP and more environments.

Great for businesses operating in the cloud.

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AI / LLM Penetration Testing

Prompt injection, ISO 42001 readiness.

Great for applications incorporating AI

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Social Engineering

Phishing, Vishing, SMShing and more.

Great for businesses with staff on the front line.

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Mobile Application Pen Testing

Customer-facing apps, portals and API layers.

Great for apps on IOS & Android

Still not certain? Tell us what you’re building and we’ll scope it with you on a 15-minute call.

When do you need an AI penetration test?

AI penetration testing isn’t a one-off box to tick. AI systems evolve constantly, and so do the attacks against them. You should consider a test when:

  • You’re launching an AI feature or product: test before it’s exposed to real users and real attackers, not after.
  • You’re giving an AI access to data or tools: the moment your model can read sensitive data or take actions, the risk changes completely and needs testing.
  • You’re building an AI agent: agentic systems that act autonomously carry some of the highest stakes in AI security today.
  • You’re working towards ISO 42001 or other governance frameworks: independent testing gives you the evidence auditors and stakeholders expect.
  • A customer or partner is asking for it: enterprise procurement increasingly requires proof that your AI has been independently tested.
  • You’ve changed your model, prompts, or data sources: even small changes can open new vulnerabilities in an AI system.
  • You’ve had an incident or near miss: if your AI has behaved in a way it shouldn’t, it’s time to understand why and close the gap.

Not sure which of these applies to you? A quick scoping conversation will tell you what you need, and just as importantly, what you don’t.

TRUSTED UK PENETRATION TESTERS

Contact CodeShield today to get a quote or work with us

At CodeShield, our UK penetration testing team brings 20+ years of combined expertise delivering practical, results-driven security solutions tailored to your business.

Get a FREE penetration test quote today

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AI / LLM penetration testing FAQs

How much does AI penetration testing cost?2026-07-27T10:41:57+00:00

The cost depends on scope: the complexity of your AI system, the number of models and integrations, whether agents and tools are involved, and the depth of testing required. Rather than quote a misleading flat rate, we scope every engagement individually so you only pay for testing that delivers real value. Get in touch for a tailored quote.

How does AI penetration testing support ISO 42001 compliance?2026-07-27T10:41:48+00:00

ISO 42001 is the international standard for AI management systems, and independent security testing helps evidence the controls it expects. Our testing and reporting map findings to relevant requirements, supporting your path to certification and demonstrating responsible AI governance.

Can you test third-party models like GPT, Claude, or Gemini?2026-07-27T10:41:38+00:00

Yes. Most organisations build on commercial models rather than training their own, so we focus on how you’ve implemented and integrated that model, your prompts, data connections, guardrails, and permissions, which is where the risks you can actually control live.

Do you test the model or the application around it?2026-07-27T10:41:27+00:00

Both. A secure model in an insecure application is still a risk, and vice versa. We assess the model’s behaviour, the application logic, the data pipelines, any connected tools or agents, and the supporting infrastructure, giving you a complete picture.

What is prompt injection?2026-07-27T10:41:18+00:00

Prompt injection is the most significant vulnerability affecting LLM applications. It occurs when crafted input, either directly from a user or hidden inside content the model processes, manipulates the model into ignoring its instructions or behaving in unintended ways. Testing for it is a core part of every AI engagement we run.

How is AI penetration testing different from traditional penetration testing?2026-07-27T10:41:07+00:00

Traditional testing targets code, infrastructure, and known vulnerability classes. AI penetration testing adds the behaviour of the model itself, testing how it can be manipulated, what it can be made to reveal, and what it can be tricked into doing. It requires a different mindset and adversarial techniques that standard tools and tests don’t cover.

What is AI penetration testing?2026-07-27T10:40:55+00:00

AI penetration testing is a security assessment of the systems you build around artificial intelligence, particularly large language models. It focuses on the risks unique to AI, such as prompt injection, data leakage, and models being manipulated into unsafe behaviour, alongside the security of the application and infrastructure around them.

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