CREST Penetration Testing

Trusted by UK Enterprises Who Take Security Seriously

Worried your systems aren’t as secure as you think?

When compliance deadlines, client demands, or recent threats raise the pressure, our CREST-certified ethical hackers help you find vulnerabilities, before attackers do. From web apps and cloud platforms to physical sites, we simulate real-world attacks so you can strengthen defences with confidence.

Custom testing for web apps, cloud, infrastructure & more

Proven 5-step testing process with real attack pathways

UK-based CREST-certified team

Cyber Essentials Plus certified

Build knowledge with interactive report & delivery workshop

Support compliance requirements such as GDPR

Certificationser Essentials Plus Certification

What are Pen Test Services

Testing Areas

When to get tested

Benefits

Methodology

Pen Test FAQs

Why Stripe OLT

Our
Awards

Megabuyte Top 50 Emerging Companies 2024

computing-cloud-excellence-awards-2021-winner-msp

computing-cloud-excellence-awards-2022-winner-2022

techreviewerco-top-it-services-companies-2021-1

This web app assessment has been vital to our business. Not only were we taken through any potential risks, but we were also given thorough guidance on how to mitigate them, in a language we were able to understand. Being given this information has been invaluable in ensuring our data is protected.

Coller Capital

Sandeep Grewal – Senior Cyber Security Manager

What Penetration Testing Really Means
& Why It Matters for Your Business

What are Pen Testing Services?

Penetration testing is an offensive security assessment conducted by cyber security experts who conduct ethical hacking to uncover and exploit potential vulnerabilities within an organisation’s technical systems. These controlled tests involve a thorough examination of various IT environments – from network infrastructure and web applications to user endpoints and even employee behaviours – all to identify and assess exploitable technical and security gaps.

By simulating real-world cyber-attacks, penetration testing provides a clear, actionable view of your organisation’s security posture. The outcome? A detailed roadmap to strengthen defences, reduce risk, and enhance overall cyber security resilience.

Get in touch about our pen test services

Our Penetration Testing Services:
Designed Around Your Risks

With so many types of penetration testing services and solutions available, it’s no surprise that many organisations aren’t sure where to start – or which approach will best suit their environment. That’s why we offer a wide range of penetration testing options, designed to cover both cloud-based and on-premises IT systems.

Some clients opt for a single targeted test; others combine multiple testing types for broader coverage. Whatever your needs, our ethical hackers will tailor a penetration test that aligns with your infrastructure, risk profile, and security goals.

Internal & External Network Penetration Test

See your Infrastructure the Way Attackers Do

Our network penetration testing service evaluates the security of your organisation’s internal and external infrastructure by simulating real-world cyber-attacks, both from within and outside your network perimeter.

Our network penetration testing service will:

Identify vulnerabilities across both external internet-facing and internal assets, including IP addresses, cloud systems and exposed ports, services and unprotected devices.

Evaluate the security and configuration of key infrastructure components such as firewalls, VPNs, routers, switches, and IDS/IPS.

Detect risks from misconfigurations, outdated software, weak segmentation, and insecure encryption practices.

Identify vulnerabilities across both external internet-facing and internal assets, including IP addresses, cloud systems and exposed ports, services and unprotected devices.

Reveal potential for lateral movement, privilege escalation, and breaches of trust boundaries.

Find out more about network penetration testing

Web Application Penetration Testing

Protect Your Customer-Facing Systems Before Hackers Find a Way In

Our web application (website) testing service identifies security risks resulting from insecure development practices. We target applications that involve frequent user interaction, where vulnerabilities in design, code, or plugins can lead to serious data breaches, unauthorised access, or full system compromise.

Our web app penetration testing service will:

Test user authentication to verify security across a variety of account types and privilege levels

Assess your web applications (Websites) for common vulnerabilities, such as Cross Site Scripting (XSS), SQL injection, broken authentication, weak APIs and server-side attacks

Help safeguard web server security and database server security posture

Align with industry standards, including the OWASP Web Security Testing Guide (WSTG) and focus on identifying the OWASP Top 10 vulnerabilities.

Provide a complete report – complete with actionable insights, a prioritised remediation roadmap, and clear guidance to strengthen your web app’s security.

Find out more about web app pen testing

Mobile Application Testing

Keep Your Users’ Data Safe on Every Device

Our mobile application penetration testing service assesses mobile and tablet applications developed for Android, iOS, and other operating systems. We test against recognised security vulnerabilities and emerging threats that frequently impact mobile app architectures.

Our mobile application penetration testing service will:

Uncover insecure app functionality and misconfigurations, such as insufficient cryptography, improper platform usage, and APIs vulnerable to server side injections

Exploit and find potential weaknesses in your application(s), like insecure data transmission and weak authorisation and authentication controls.

Support and safeguard your software development lifecycle, through continuous integration of security practices.

Evaluate application security controls, such as root/jailbreak detection, certificate pinning, and code obfuscation.

Our testing aligns with industry standards, including the OWASP Web Security Testing Guide (WSTG) and focuses on identifying the OWASP Top 10 vulnerabilities.

Provide a comprehensive report, complete with actionable insights, a prioritised remediation roadmap, and clear guidance to strengthen your app security.

Find our more about mobile pen testing

Cloud Penetration Testing

Secure Azure, AWS & GCP Environments the Right Way

Cloud pen testing services will:

Detect weak credentials, misconfigured IAM roles, and insufficient access controls.

Identify server misconfigurations, insecure APIs, exposed storage, and other common cloud missteps.

Discover outdated software and unpatched services vulnerable to exploitation.

Assess the security of cloud-native components such as containers, serverless functions, and exposed endpoints.

Evaluate your implementation of the shared responsibility model and pinpoint areas where your obligations may be at risk.

Provide a complete report, with actionable insights, a prioritised remediation roadmap, and clear guidance to strengthen your cloud environment.

Find out more about cloud pen testing

Wireless Penetration Testing

Stop Attackers at the Network Edge

Our wireless penetration testing service is designed to identify and assess vulnerabilities in the connections between all endpoints and devices linked to your organisation’s Wi-Fi network. This includes desktops, laptops, smartphones, and Internet of Things (IoT) devices.

Wireless security testing services will:

Identify security vulnerabilities in your wireless infrastructure, including weak access point configurations, outdated firmware, and misconfigured devices.

Detect rogue or unauthorised access points and devices attempting to connect to your network.

Evaluate the strength and implementation of wireless encryption protocols (e.g., WEP, WPA, WPA2) and identify weak or deprecated configurations.

Gain insight into how an attacker could navigate through your wireless network, escalate privileges, and gain deeper access into your infrastructure.

Provide a complete report, with actionable insights, a prioritised remediation roadmap, and clear guidance to strengthen your wireless security posture.

Learn more about wireless pen testing

API Penetration Testing

Lock Down the Hidden Gateways Behind Your Apps

Our API Penetration Testing service simulates real-world attacks to uncover vulnerabilities in the backbone of modern applications – your APIs. This ensures secure data exchange, robust access controls and alignment with regulatory compliance.

API security testing services will:

Identify common vulnerabilities such as broken authentication, authorisation flaws, injection risks, and excessive data exposure, guided by OWASP API Security Top 10.

Assess access control mechanisms, including API keys, tokens, and OAuth2 implementations, for misconfigurations or bypass risks.

Validate input handling and error messaging to detect injection flaws and information leaks, and potential data integrity issues.

Analyse business logic for exploitable workflows, such as privilege escalation or bypassing validation steps.

Provide a comprehensive report, with actionable insights, a prioritised remediation roadmap, and clear guidance to strengthen your APIs.

Get in touch about our pen test services

Physical Penetration Testing

Because Locks and Doors Are Still Entry Points

Our Physical Penetration Testing service simulates real-world intrusions to evaluate your organisation’s physical security controls. By finding and addressing physical vulnerabilities, we help protect your people, assets, and sensitive information.

Our physical security testing service will:

Assess perimeter defences by identifying unsecured entry points, testing locks and access controls, and assessing surveillance systems.

Deliver Intrusion Simulation with methods such as tailgating, lock picking, and bypassing security barriers to gain entry into restricted areas.

Test internal security by trying to get into sensitive areas like server rooms, checking visitor protocols and testing employee adherence to security policies.

Find information leakage risks through techniques like dumpster diving, shoulder surfing and inspecting unattended workstations for sensitive data exposure.

Provide a complete report with actionable insights and a prioritised roadmap to strengthen your physical security posture.

Get in touch about our pen test services

Infrastructure Penetration Testing

Protect Your Customer-Facing Systems Before Hackers Find a Way In

Our Infrastructure Penetration Testing service tests your organisation’s internal and external IT systems to find weaknesses from on-premise servers to virtual environments and core networking assets.

Our Infrastructure pen testing service will:

Find vulnerabilities in internal and external components, including servers (Windows/Linux), virtual machines, workstations, databases, active directory networks public-facing infrastructure.

Discover misconfigurations, exposed services, outdated software, insecure interfaces and weak user permissions across systems like firewalls, remote access tools and internal protocols.

Test segmentation, access controls and privilege escalation risks, simulating threats from external attackers and insider threats or compromised internal accounts.

Test your organisation’s ability to detect and respond to malicious activity, validate internal monitoring and incident response procedures.

Provide a complete report with actionable insights and a prioritised roadmap to strengthen your infrastructure security posture.

Learn more about infrastructure pen testing

Other Testing Areas

Go beyond with testing designed for niche areas

Many more areas of penetration testing services are available, each designed and tailored to identify different security weaknesses. Stripe OLT can help you with tailored pen tests in these areas:

Some additional penetration areas we can accommodate include:

Email server

Servers

Firewalls

Software

Active Directory

Azure AD

Application and code

Database systems

Authentication and identity management

Compliance-driven testing

Get in touch about our pen test services

When and How Often Should You Carry Out a Pen Test?

Penetration testing shouldn’t be a one-time exercise. To maintain a strong security posture, organisations should schedule tests regularly and in response to key business or technical changes.

After Infrastructure Changes

When deploying new systems, networks, or cloud environments.

Following Major Software Deployments

After launching new applications or applying significant updates.

Post-Security Incident

To identify exploited vulnerabilities and prevent repeat attacks.

During Mergers & Acquisitions

To assess and secure integrated infrastructure and applications.

To Meet Compliance Requirements

Required or recommended under frameworks like ISO 27001, GDPR and DSP TOOLKIT.

When Entering New Markets or Sectors

To address evolving or industry-specific threat landscapes.

As Part of a Regular Security Program

Annual, semi-annual, or quarterly testing helps maintain ongoing resilience and risk visibility./row

A Smart Investment, The Benefits of Penetration Testing

Identify Security Weaknesses

Simulate real-world cyberattacks to uncover vulnerabilities in your networks, applications, and systems – before threat actors can exploit them.

Improve Your Security Posture

Receive actionable insights to strengthen defences and stay ahead of emerging cyber threats.

Comply with Regulations

Support compliance with industry standards such as GDPR or ISO 27001 by regularly testing your security controls.

Protect Business-Critical Assets

Safeguard sensitive data and critical systems by identifying and remediating security gaps that could lead to breaches.

Reduce Costs Through Early Detection

Addressing vulnerabilities early helps prevent costly security incidents – making penetration testing a cost-effective part of your cyber security strategy.

Be Incident Response Ready

Test and strengthen your incident response plans to ensure fast, effective reactions to potential security events.

Demonstrate Security Commitment

Show stakeholders, partners, and customers that you take cyber security seriously – building trust and credibility.

Support Continuous Improvement

Regular penetration testing helps you adapt to the evolving threat landscape and continuously improve your cyber resilience.

Test Security Controls Effectively

Validate whether your existing security tools, configurations, and policies are performing as intended.

Strengthen Risk Management

Inform your risk assessments by identifying, prioritising, and addressing vulnerabilities based on real-world threats.

What our Clients Say

Pre-engagement Scoping and Preparation

Before testing begins, we work closely with your team to define the scope, objectives, and testing boundaries. This ensures clarity on what will be tested, when, and how. All aligning the assessment with your business priorities and compliance requirements.

Reconnaissance & Information Gathering

We gather information about your environment, infrastructure and publicly available data. This phase identifies potential targets and helps shape our threat model so the test mirrors real world attack scenarios.

Scanning & Enumeration

We use manual penetration testing techniques and industry leading tools to scan your systems to find vulnerabilities, misconfigurations and exposed services. We also enumerate services, applications and infrastructure components to get deeper into your environment.

Access & Exploitation

Our team simulates targeted malicious attacks to gain access through the identified vulnerabilities. We test how an attacker could get into your systems, escalate privileges and access sensitive data – all without disrupting business.

Expansion & Access Maintenance

We test how far access can be expanded within your systems, how long it can be maintained undetected and what the impact of a sustained breach would be. This phase highlights immediate risks and long-term security gaps.

Reporting

Once testing is complete we ensure your environment is restored to its original state. We provide a clear, jargon free report of all findings, business impact and actionable steps to improve your security posture.

Why Choose Stripe OLT for you pen testing needs?

Accreditations

Accreditations & Standards

We are a CREST-certified penetration testing provider, delivering assessments that meet rigorous industry standards and ethical testing practices.

Our work follows ISO 27001-certified processes, ensuring all data handling, testing methods and reporting are managed securely throughout every engagement.

We also support organisations in achieving and maintaining Cyber Essentials and Cyber Essentials Plus, identifying vulnerabilities and guiding remediation to help you meet certification requirements confidently.

Microsoft Expertise

Microsoft-first Security Expertise

As a Microsoft Security Solutions Partner with security specialisations in Cloud Security and Threat Protection we have deep expertise in Microsoft 365, Azure and hybrid cloud environments, so we can deliver relevant assessments across modern infrastructure.

UK- Based Experts

UK-based Experts with Sector Experience

Our UK-based security team bring extensive real-world experience, and our team was one of the first globally to achieve the updated CREST SOC accreditation, a benchmark of excellence in modern threat detection and response.

We also understand the unique risks and regulatory pressures across finance, healthcare, education, legal and other regulated sectors, ensuring your penetration testing aligns with industry-specific compliance and threat landscapes.

Accreditations

Testing Approach & Engagement Options

Blended Manual and Automated Testing
We combine automated scanning with deep manual testing to find more security flaws. Automation finds common weaknesses, while our manual testing finds complex threats including business logic flaws, misconfigurations, input validation issues, authentication or authorisation gaps and more that automated tools miss.

Continuous or One-off Testing
We can deliver both one-time penetration tests for compliance or project needs, or ongoing testing programmes for continuous threat monitoring and assurance.

Managed Cyber Security FAQs

Penetration Testing Basics

Why should I do a penetration test?

Penetration testing helps you stay ahead of attackers by identifying and fixing vulnerabilities before they can be exploited. As businesses rely more heavily on digital systems and cloud platforms, the risk of sophisticated cyberattacks is only increasing.

Regular penetration testing protects not just your organisation, but your customers too which ensures that sensitive data, systems and services aren’t left exposed.

It’s also becoming a critical requirement for many sectors, particularly finance, legal and healthcare, where compliance with frameworks like ISO 27001, GDPR or Cyber Essentials Plus is essential.

At Stripe OLT, we help organisations test their defences, meet regulatory demands, and reduce the risk of reputational and financial damage through our certified CREST penetration testing services.

What is the difference between white, black and greybox testing, and do you have a recommendation as to which one I should pick?

The difference comes down to how much access and information the penetration tester is given:

White box testing gives full access, including credentials, documentation, and sometimes source code, to uncover as many issues as possible.
Black box testing simulates a real-world attacker with minimal knowledge, usually just a URL or IP address.
Grey box sits in between; penetration testers might be given user-level access or credentials, but not full insight into the backend.

The right choice depends on what you’re trying to achieve.

Want a deep, thorough assessment? Go white box.
Want to see what an external attacker could realistically do? Choose black box testing.
Looking for a balanced, practical approach? Grey box is often ideal, and it’s what we typically recommend for things like web apps.

At Stripe OLT, we help you choose the method that fits your goals, infrastructure, and risk level.

What are the stages of pen testing?

The stages of penetration testing can vary depending on the provider, the type of test, and the complexity of your environment. Different companies use different methodologies, and at Stripe OLT, we follow a five stage approach.

As outlined earlier on this page, our typical process includes:

Pre-engagement scoping and preparation: We work with your team to define the scope, objectives, and boundaries, aligning the test with your business and compliance requirements.
Reconnaissance & information gathering: Our team gathers intelligence about your environment to shape realistic, attacker-style scenarios.
Scanning & enumeration: Using both manual techniques and industry-leading tools, we expose vulnerabilities, misconfigurations, and exposed services.
Access & exploitation: We simulate targeted attacks to test how vulnerabilities could be used to gain access, escalate privileges, and compromise sensitive data.
Expansion & access maintenance: We assess how far an attacker could go undetected, and what the impact of an extended breach could look like.
Reporting, you receive a clear, actionable report with business impact, prioritised findings, and remediation steps.

Where agreed, we also support:

Retesting to confirm vulnerabilities have been successfully addressed

While no two tests are exactly the same, our methodology ensures consistency, transparency, and results you can act on, get in touch to find out how our pen testers can help you.

How often should penetration testing be done?

We recommend penetration testing as part of your ongoing cyber security strategy, not a one-off.

At a minimum, most organisations benefit from annual testing, but frequency should be driven by risk, compliance, and change. For example:

After major infrastructure or application changes
After a security incident
Before launching new digital services
During mergers or acquisitions
To meet compliance standards like ISO 27001, Cyber Essentials Plus, or GDPR

For some high-risk or regulated environments, quarterly or bi-annual testing may be more appropriate, especially where systems are critical or frequently updated.

At Stripe OLT, we help organisations define a testing schedule that fits their risk profile, industry requirements and security maturity.

Planning & Scoping Your Test

Which penetration test service should I choose?

In our opinion, the right penetration test isn’t one size fits all; it’s all about your organisation’s structure and compliance requirements.

If you’re in a highly regulated industry like finance or healthcare, you’ll likely need a test aligned to specific frameworks like ISO 27001, GDPR or Cyber Essentials Plus. For hybrid environments or those heavily using Microsoft 365 and Azure, we’d recommend starting with cloud and external infrastructure testing. And if you have customer-facing apps or portals, web application testing is usually the priority.

At Stripe OLT, we help businesses scope the right approach, whether that’s a single test or a blended assessment across multiple testing areas.

If you’re not sure where to start, talk to us, we’ll help you define the right scope for your organisation, goals, risks and regulatory obligations.

What information do I need to provide for a pen test?

To get the most value from a penetration test, it’s important to provide a clear and accurate picture of your environment. We always start with a structured scoping session to define what’s being tested and how.

What you need to provide will partly depend on whether the test is black box, grey box, or white box:

Black box testing simulates an external attacker with no prior knowledge, so we typically only need public-facing details (like IPs or URLs).
Grey box testing involves some internal knowledge, like user credentials or limited access, and gives us a deeper view into application logic and internal controls.
White box testing is the most comprehensive; it may require full documentation, admin access, configurations, or source code, depending on what’s being tested.

Beyond that, we’ll usually ask for:

A list of assets or systems to be tested
Technical contacts for coordination
Any areas to exclude (e.g. production systems during critical periods)
Compliance goals (e.g. Cyber Essentials Plus, ISO 27001, GDPR)
Recent changes or past incidents (to identify areas of concern)

Don’t worry if this feels overwhelming. Get in touch, and we can guide you through it all and help define the right scope for your business.

How long does it take to conduct a penetration test?

This is dependent on the kind of test being performed.

For example, 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 or phased approaches can require several weeks to complete.

At Stripe OLT, we define clear timelines during the scoping process and include time for both testing and delivery of your detailed report and remediation workshop.

Will my organisation be disrupted by a penetration test?

There is some risk with penetration testing, but when scoped and managed correctly, disruption is very rare. At Stripe OLT, we take every precaution to not impact live systems, and work closely with your team to make sure everything runs smoothly.

Before we start testing, we will:

Agree on safe test windows
Identify critical systems to exclude
Flag potential weak points where downtime could occur, so you’re fully informed
Secure secondary approval for any high-risk test cases

If anything unusual is found, by us or your team, open communication is key. We’ll stop testing immediately and work with you to figure out what’s going on. If needed, we’ll also provide relevant logs to your internal teams.

Testing Options & Costs

Can I get a one-time pen test, or do I need continuous testing?

You can do a one off penetration test, and for many organisations, this is the right place to start. It’s useful for compliance, testing a new system or responding to a recent change.

But for businesses with dynamic environments, such as cloud platforms or frequent software releases, we recommend considering continuous or scheduled testing. This means regular, automated and manual testing to catch new vulnerabilities as they emerge, so you can stay ahead of the game.

At Stripe OLT, we’ll tailor the approach to your risk profile and budget, whether that’s a one-off or a longer-term testing strategy.

How much does a penetration testing service cost?

There’s no fixed price for penetration testing, because the 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:

The number of hours needed for testing and analysis
The complexity or criticality of the systems involved
Any travel or on-site requirements
Reporting time, QA, and final delivery workshops
Licensing or tooling required for the specific engagement

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’d like a tailored quote based on your environment and goals, get in touch. We’d be happy to help you scope it out so you don’t over pay for what you don’t need.

What tools are used during a penetration test?