CREST Penetration Testing Services For London organisations

Real-world testing for London organisations.

Worried your systems are not as secure as you think? When compliance deadlines, client demands, recent threats or major technology changes raise the pressure, our CREST certified ethical hackers help you find vulnerabilities before attackers do.

From web applications and cloud platforms to infrastructure, wireless networks and physical sites, we simulate real-world attacks so you can strengthen defences with confidence.

Custom testing for web apps, cloud, infrastructure, wireless, physical sites and more

Cyber Essentials Plus certified organisation

Proven testing process built around real attack pathways

Build internal knowledge with an interactive report and delivery workshop

UK-based CREST certified team

Support compliance requirements such as GDPR, ISO 27001, PCI DSS and supplier assurance

Our
Awards

“The assessment reinforced how quickly the threat landscape is changing, and has helped us understand and mitigate potential risks. If I had one piece of advice for someone who has never undertaken a pen test, it would be: do it before it’s too late.”

Coller Capital

Sandeep Grewal, Coller Capital

Why Penetration Testing is Essential for London organisations

London businesses face an increasingly hostile cyber threat landscape, with 51% of London organisations identifying breaches or attacks compared to the UK average of 43%. With the National Cyber Security Centre recording 204 nationally significant cyber attacks in the year to September 2025, proactive vulnerability identification is becoming essential for London organisations handling sensitive, regulated or business-critical data.

For London’s financial services, legal, healthcare, public sector and green energy organisations, penetration testing helps validate security controls, support compliance requirements and reduce the risk of costly disruption. With over 20 years of experience, Stripe OLT’s CREST certified penetration testers deliver real-world security assessments that help organisations identify weaknesses before attackers can exploit them.

Get in touch about our pen test services

Who Our Penetration Testing Services Are For

Our penetration testing services are suitable for London based organisations that need independent assurance over their systems, applications, infrastructure or physical security controls. This includes:

Financial services firms with regulatory or client assurance requirements

Legal practices handling confidential client data

Healthcare and public sector organisations protecting sensitive information

Mid-market organisations introducing new systems, applications or cloud environments

SMEs needing supplier assurance, cyber insurance support or evidence of security testing

IT and security teams seeking independent validation of existing controls

Whether you need managed SOC monitoring, incident response support, penetration testing, Cyber Essentials guidance, user training or a Microsoft 365 security review, we help define the right cyber security solutions based on your risks, goals and environment.

Speak to
OUR Experts

Discover what we can do for your business.

Our Top 10 Penetration Testing Areas

1. Network Penetration Testing

Internal and external network testing across exposed services, ports, segmentation and access routes to identify weaknesses in your network infrastructure.

Discover Network Pen Testing

2. Infrastructure Penetration Testing

Testing of servers, workstations, databases, Active Directory, cloud infrastructure and core business systems to uncover security flaws in your IT infrastructure.

Discover Infrastructure Pen Testing

3. Web App Penetration Testing

Web application penetration testing against OWASP Top 10 vulnerabilities and custom application security flaws, using both automated tools and manual techniques.

Discover Web App Pen Testing

4. Cloud Security Penetration Testing

Azure, AWS and GCP penetration testing for London cloud users, examining configuration, identity management and privilege escalation paths in cloud environments.

Discover Cloud Pen Testing

5. Social Engineering Penetration Testing

Phishing simulations and staff awareness evaluation that test human intelligence vulnerabilities and security team response to evolving threats.

Discover Social Engineering Pen Testing

6. Mobile Application Penetration Testing

iOS and Android app security assessment for mobile apps, identifying security vulnerabilities in application penetration testing scenarios.

Discover Mobile App Pen Testing

7. Wireless Penetration Testing

WiFi and network access point vulnerability analysis to identify security gaps in wireless infrastructure.

Discover Wireless Pen Testing

8. Physical Penetration Testing

On-site security controls and access management testing that examines physical security weaknesses alongside technical controls.

Discover Physical Pen Testing

9. API Penetration Testing

REST and SOAP API vulnerability identification, ensuring your web apps and integrations resist emerging threats.

Discover API Pen Testing

10. LLM/AI Penetration Testing

Testing of standalone and integrated AI applications for prompt injection, guardrail bypass, data leakage and insecure model or agent workflows.

Discover LLM/AI Pen Testing

Our Penetration Testing Methodology

Our tested process is structured enough to give clarity, but flexible enough to reflect the systems, applications, offices or cloud environments being tested.

Step 1: Pre-engagement Scoping and Preparation

We confirm the assets in scope, exclusions, testing windows, key contacts and any compliance or assurance requirements. This gives your team a clear view of how the engagement will run before work begins.

Step 2: Reconnaissance and Information Gathering

We build a picture of your external exposure, internal systems, applications, access routes and relevant business context. This helps focus the assessment on the areas where compromise could have the greatest impact.

Step 3: Scanning and Enumeration

We use manual techniques and specialist tools to identify vulnerabilities, misconfigurations, exposed services and system details that need further validation. Where appropriate, AI-assisted analysis may support the process, but testing remains consultant-led and manually validated, with client data kept separate from AI tools.

Step 4: Access and Exploitation

We safely test whether identified weaknesses can genuinely be used by an attacker, including possible access routes, privilege escalation, data exposure and wider compromise paths.

Step 5: Expansion and Access Maintenance

We assess how far an attacker could move through the environment, whether access could be maintained and what this would mean for your organisation’s risk profile.

Step 6: Reporting

Once testing is complete, we restore the environment to its original state. You receive a clear report, practical remediation guidance, a delivery workshop and optional retesting where agreed.

What our Clients Say

Frequently Asked Questions

How often should London organisations conduct penetration testing, and when should they arrange one?

High-risk sectors like finance or healthcare should conduct penetration tests quarterly or after major changes, while most organisations should test at least annually for compliance with GDPR, PCI DSS or ISO 27001. London businesses often require more frequent, in-depth penetration testing, sometimes on a semi-annual basis. Regular penetration testing is recommended at least once a year or after large changes to infrastucture to identify and address vulnerabilities. Arrange penetration testing after:

After infrastructure changes, new networks or new cloud environments
Following major software deployments or significant updates
After a security incident to identify exploited weaknesses
During mergers and acquisitions
To support ISO 27001, GDPR, DSP Toolkit or supplier assurance requirements
When entering new markets or regulated sectors
As part of a regular security programme addressing future testing requirements

Penetration testing should be part of a continuous security management strategy, incorporating monitoring and regular updates to patch systems. Where appropriate, we can also help design a structured testing programme aligned to your annual security and risk strategy.

What certifications do your penetration testers hold?

Hiring accredited professionals is crucial for quality penetration testing. Our cyber security professionals hold penetration testing-specific certifications including CREST security testing, OSCP (Offensive Security Certified Professional), CRTO (Certified Red Team Operator) and CRTL (Certified Red Team Lead). Continuous professional development ensures expertise against offensive security challenges and evolving threats.

Additionally, GIAC Security Essentials Certification, ISO 27001, Cyber Essentials, Cyber Essentials Plus and our Microsoft Solutions Partner for Security status, including cloud security and threat protection specialisations, provide additional trust signals for our organisation. Together, these credentials strengthen our wider security capability, giving our clients the confidence that we deliver penetration testing from a mature, well-governed cyber security practice.

Can penetration testing be conducted remotely for London offices?

Most infrastructure testing and application penetration testing can be performed remotely with minimal disruption to your business operations. This approach is suitable for network penetration testing, web application testing, cloud security testing and API assessments.

On-site testing remains available for physical penetration testing and some wireless network assessments. We offer flexible scheduling to accommodate London business hours and ensure security testing minimises impact on your operations.

Do you use AI to conduct penetration testing?

Penetration testing at Stripe OLT remains consultant-led. AI may be used in controlled ways to support analysis, efficiency or internal review, but it does not perform the assessment, make final risk decisions or replace manual validation by our penetration testers.

We do not upload client data into public AI tools as part of testing. Our approach is designed to go beyond automated checkbox testing, with clear scoping, human-led validation and practical remediation guidance. AI use does not create open-ended token-based costs for clients.

How long does a typical penetration test take?

This depends on the type of penetration test being performed. A web application penetration test typically takes around one week, including both testing and reporting. A cloud configuration review may take no more than two days.

More complex, bespoke testing or assessments involving multiple assets, environments or phased approaches can require several weeks to complete.

At Stripe OLT, clear timelines are defined during the scoping process and include time for testing, detailed report delivery and a remediation workshop.

How much does a penetration testing service cost?

There is no fixed price for penetration testing, because cost is shaped by the type of test, the size and complexity of your environment, and the level of depth required.
At Stripe OLT, our pricing is built around a transparent, scoped model, taking into account factors such as:

Number of domains, systems, applications or assets in scope
Duration of discovery, testing and analysis
System architecture and environment complexity
Complexity or criticality of the systems involved
Depth of required threat intelligence review
Any travel or on-site requirements
Reporting requirements, QA and final delivery workshop time
Licensing or tooling required for the specific engagement

We provide fixed-scope pricing, clearly defined assumptions and deliverables, and no hidden costs or unexpected add-ons.
Rather than offering a one-size-fits-all quote, we work with you to define the right scope and ensure the cost reflects both the value delivered and the risk reduced. If you would like a tailored quote based on your environment and goals, get in touch and we can help scope it out so you do not overpay for what you do not need.

Contact Stripe OLT for Penetration Testing in London

Get Your Security Assessment Started

Stripe OLT provides penetration testing services to organisations across the UK, including web application, infrastructure, cloud, mobile, wireless and network penetration testing. For London businesses, our local office details are listed below, with support available from our UK-based CREST-certified testing team.

London phone: +44 (0) 207 043 7044

London office: 29 High Holborn, London, WC1V 6AZ

Request your online quote today. Emergency incident response availability for organisations requiring immediate support.

CREST Penetration Testing Services For London organisations

Our Awards

Coller Capital

Why Penetration Testing is Essential for London organisations

Who Our Penetration Testing Services Are For

Speak to OUR Experts

Our Top 10 Penetration Testing Areas

1. Network Penetration Testing

2. Infrastructure Penetration Testing

3. Web App Penetration Testing

4. Cloud Security Penetration Testing

5. Social Engineering Penetration Testing

6. Mobile Application Penetration Testing

7. Wireless Penetration Testing

8. Physical Penetration Testing

9. API Penetration Testing

10. LLM/AI Penetration Testing

Our Penetration Testing Methodology

Step 1: Pre-engagement Scoping and Preparation

Step 2: Reconnaissance and Information Gathering

Step 3: Scanning and Enumeration

Step 4: Access and Exploitation

Step 5: Expansion and Access Maintenance

Step 6: Reporting

What our Clients Say

Geo

Coller Capital

Frequently Asked Questions

Contact Stripe OLT for Penetration Testing in London

Get Your Security Assessment Started

Our
Awards

Speak to
OUR Experts