The Ultimate Guide to Penetration Testing: How to Strengthen Your Cyber Defences

Cyber threats continue to increase in volume and sophistication, leaving organisations more vulnerable than ever. For IT Directors, CISOs, and security professionals, ensuring a robust security posture isn’t just good practice anymore – it’s a necessity to keep your business safe.

In this guide, we’ll explore what penetration testing is, why it’s essential, and how to choose a trusted penetration testing service provider. Whether you’re looking for a 3rd party penetration testing partner or simply want to understand the process, this guide will give you the insights you need to strengthen your security posture.

What Is Penetration Testing?

Penetration testing – (also known as pen testing and ethical hacking) – is described as a simulated cyberattack against your networks, web applications and systems. Penetration Testing will identify any weaknesses or potential security vulnerabilities in your security systems.

According to the National Cyber Security Centre (NCSC), penetration testing is:

“A method for gaining assurance in the security of an IT system by attempting to breach some or all of that system’s security, using the same tools and techniques as an adversary might.”

Pen testing is the best method to identify any vulnerabilities or risks to the business and take action before a breach occurs.

What is the main purpose of penetration testing?

Penetration testing services help businesses to identify, diagnose, and patch or remedy network, system and web app vulnerabilities or mobile app vulnerabilities before they can be exploited by malicious hackers.

A penetration test should be thought of in the same way as a financial audit for your business. But instead of looking at invoices and accounts, it’s a security exercise where a cyber security expert attempts to find and exploit vulnerabilities.

The purpose of pen testing is to test the strength of your cyber defences. It helps identify:

Where a hacker might gain access
How effective your current security controls are
The potential business impact of a breach
Whether staff, systems, and applications are secure

This approach gives you a clear understanding of your organisation’s cyber risk, and helps you fix the issues before they’re exploited.

Difference between Pen Testing and vulnerability scanning

Penetration testing is entirely different from a vulnerability scan. But the two often are confused.

Pen testing takes the approach of an authorised, simulated attack on a company’s computer systems, applications or network. A vulnerability scan simply uses IP addresses to search for any known vulnerabilities. This can even be executed by just using a piece of software.

Penetration testing will provide a much more comprehensive view of current security risks. Think of penetration testing as picking up from where the vulnerability assessment ends, to attempt to gain access and infiltrate like a hacker would.

Why Your Organisation Needs Penetration Testing

Companies with 250–5000 employees are often seen as high value targets by attackers. At this size of business, balancing growing infrastructure with limited security resources, they are the ideal candidate for regular testing.

Penetration testing looks for a range of issues and vulnerabilities in your systems and networks. The insights provided by penetration testing can be used to fine-tune security policies as well as address vulnerabilities with patching and other remediation.

Insecure setup or configuration of networks
Security testing experts will try to breach your systems by looking for weak passwords and exploiting any vulnerabilities to open ports, unpatched applications and incorrectly set user privileges.

Incorrect encryption and authentication
Testers will assess whether data is encrypted to a sufficient level, for example in line with article 32 of the GDPR (General Data Protection Regulations) policy, which outlines appropriate technical measures to secure data.

Code and command injection
The testers will check that any web forms are built to protect against SQL injection attacks and find how they behave when someone tries to breach them.

Session management
Tools and methodology will be used to assess if your cookies and sessions tokens are susceptible to exploitation for malicious use.

Key business drivers for Penetration Testing Services

Compliance: Frameworks like ISO 27001, PCI DSS, and GDPR increasingly expect Pen Testing as part of best practice.
Customer confidence: Clients expect their data to be safe. By conducting pen testing, you show that you take that responsibility seriously.
Threat awareness: Understand where the risks lie and how to defend against them.
Risk reduction: Reduce the chance of a successful attack and the cost of a breach.

By engaging a 3rd Party Penetration Testing provider like DigitalXRAID, you gain independent, expert insights into your defences and reduce the risk of internal bias.

Types of Penetration Testing Explained

As technology advances and the ways and means that cybercriminals use to gain access to your networks, systems, and applications proliferate, so do the types of penetration testing.

Internal vs External Pen Testing

Internal Penetration Testing simulates an attacker with access to your internal network – such as a disgruntled employee or a breached device.

External Penetration Testing simulates an attacker from the outside trying to access your public facing systems.

Black Box vs White Box Testing

Understand the testing scope with these approaches:

Black Box Testing – no prior knowledge is given to the tester. This mimics a real world hacker. Learn more

White Box Testing – the tester has full knowledge of your systems, often used to assess how deep vulnerabilities go. Learn more

Key Types of Penetration Testing Services

These are some of the most common types of penetration testing services available to test the security risks associated to your networks, systems and web applications, diagnosing the flaws in your security before they can be exploited.

Each type of penetration testing service can be tailored to your organisation’s size, sector, and risk profile.

Web Application Pen Testing

More than 30,000 websites are attacked every day, with more than 60% of all internet-based attacks launched against web applications. Modern web application penetration testing will find any weaknesses. Penetration testers can also check the functionality of websites to pinpoint any failings.

Regular web app pen testing will defend against every conceivable online threat.

Mobile App Pen Testing

With the increase in mobile use and mobile devices organisations must take steps to secure their mobile applications, to protect the business, its reputation and most importantly, its customers.

A mobile application penetration testing process will look for a range of exploitable vulnerabilities that cybercriminals may take advantage of.

Cloud Penetration Testing

As cloud environment use increases, so does the increase in attacks against these services. Cloud security assessments validate the security of cloud hosted environments. Any company utilising cloud environments should follow all cloud security best practices during implementation to prevent any data breaches.

Social Engineering Tests

Social engineering testing involves simulated phishing and other human targeted vectors, to manipulate people into revealing confidential information, granting access to systems, or taking actions that benefit the attacker.

Red Team Testing

Red Team Exercises are a full simulation of an adversary’s tactics, often without prior warning to staff, designed to help you proactively identify vulnerabilities and further strengthen your cybersecurity posture.

Automated Pen Testing

Some businesses have opted to conduct automated penetration testing in recent years. With budget restraints posing challenges, this has been a fallback option to enable more regular penetration testing.

How Often Should You Conduct Pen Testing?

CREST and the NCSC recommend that pen testing is conducted annually as a minimum. However, you should conduct pen testing:

After any major infrastructure or application changes
Following a merger, acquisition, or re-platforming exercise
Before launching new services or systems
After a security incident or cyber breach
Quarterly or bi-annually as part of a continuous security testing strategy

What to Expect from a Penetration Test

Penetration testing can follow different methodologies based on standards such as The OWASP (Open Web Application Security Project®) Top 10. This standard outlines the most critical security risks to web applications which a penetration tester can follow to identify any common risks and vulnerabilities that are present.

Another example is the highly respected CREST penetration testing method. CREST set out a code of conduct around preparation and scoping best practices, penetration testing execution, post testing reporting delivery and data protection. Only CREST certified penetration testing service providers can promise to conduct pen testing services to this gold standard.

A high-quality pen testing service typically includes:

1. Scoping and Planning

Agree on the objectives, targets, and the type of testing. The more thorough this stage is, the more effective the test results.

2. Reconnaissance

Pen testers gather information including DNS data, IP addresses, and system architecture, often using publicly available data.

3. Vulnerability Assessment

Using both manual and automated tools, testers run vulnerability scans to identify weak spots.

4. Exploitation

Ethical hackers simulate real attacks including using custom built exploits to expose any identified vulnerabilities, escalate privileges, and access sensitive data.

5. Reporting

You receive a detailed report that categorises risks into Critical, High, Medium, Low and Informational categories and outlines remediation steps.

6. Retesting (optional but recommended)

After any remediation fixes are applied, a follow up test ensures vulnerabilities have been resolved.

How much does penetration testing cost in the UK?

Prices vary, but most penetration testing services range from £5,000 to £25,000+ depending on scope and complexity.

How long does a penetration test take?

Typically a pen test will last for 1–2 weeks including reporting. Red Team tests may take longer.

What are the benefits of penetration testing?

Penetration testing will reveal your security weaknesses and how vulnerable your company is to cyberattack, as well as identifying potential threats to your cyber security and overall business. These findings can be used to improve your internal security management processes.

There are many benefits to be gained from penetration testing. If any weaknesses that are identified during pen testing are left unpatched, bad actors are likely to exploit and compromise the business.

The pen test report will provide a clear view of any weaknesses, so you ensure that security controls and processes are addressed. This helps to reduce information security risk and reports can be shared with senior management to improve cyber security awareness.

Penetration testing will ensure the business is continuously safeguarded. You will be able to:

Identify any security issues and remediate them with the right controls
Benchmark your existing processes and security controls
Understand where applications have developed bugs or not been patched sufficiently
Support any regulatory compliance requirements such as PCI-DSS (Payment Card Industry Data Security Standard)
Provide assurance to senior management, stakeholders, partners and most importantly customers that their data is protected

What is third party penetration testing?

3rd party penetration testing – also known in the industry as outsourced penetration testing or pen testing services – involves hiring an external pen testing company to conduct security assessments on your IT infrastructure, web apps and systems.

3rd party services are the most effective way for organisations to understand the gaps and vulnerabilities in their security posture, with the impartial view and fresh eyes that an external provider can provide.

There are many reasons that an organisation should engage with a third-party penetration testing service provider, including:

Demonstration of security best practice
Cost savings of penetration testing outsourcing vs hiring in-house
Check if there are any vulnerabilities that an in-house team has missed
A more holistic view of the threat landscape for more comprehensive testing
Access to highly skilled professionals and gold standard testing methodologies

Why Use a 3rd Party Penetration Testing Provider?

Engaging a 3rd Party Pen Testing Service provides:

Independent expertise: Internal teams may overlook risks.
Access to certified testers: Outsourcing gives access to top-tier talent.
Compliance support: Trusted vendors provide reports suitable for audits and board-level review.
Objectivity and depth: Avoids conflict of interest in self-testing.

In-house vs 3rd party penetration testing

The only way to truly understand if your business has any vulnerabilities that put you at risk of a cyberattack is to enlist a 3rd party service provider.

CREST International is quoted as saying, “There are many benefits in procuring penetration testing services from a trusted, certified external company who employ professional, ethical and highly technically competent individuals. CREST member companies are certified penetration testing organisations who fully meet these requirements, having been awarded the gold standard in penetration testing, building trusted relationships with their clients.”

Choosing the Right Penetration Testing Partner

Not all providers are created equal. Penetration testing should only be conducted by highly qualified cyber security professionals. The quality of the results that can be achieved from a penetration test is largely based on the skill that the penetration testers have.

The NCSC mandates that public sector organisations only use pen testers and cyber security service providers that are accredited as part of the CHECK scheme.

For private sector businesses, CREST penetration testing providers offer the highest standard of penetration testing security service available.

Here’s what you should look for:

Accreditations: CREST, CHECK, and CREST OVS indicate trust and external verification for added assurance

Experience: Look for proven results and pen testing case studies

Transparency: Avoid providers offering vague or automated only services

Learn more about How to choose a penetration testing provider.

At DigitalXRAID, our pen testing service is CREST and CHECK accredited, with expertise across all sectors.

Penetration Testing for Compliance

Pen Testing is often a compliance requirement and is included in frameworks such as:

ISO 27001: Pen Testing is a critical component of information security risk management.
PCI DSS: Quarterly scans and annual tests are required for merchants.
DORA: For financial entities operating in the EU, regular testing underpins resilience.
NIS2: Pen Testing supports the identification of risks for operators of essential services to protect critical national infrastructure.
GDPR: Demonstrates reasonable data protection controls in the event of a breach.

Is penetration testing mandatory for ISO 27001?

While not explicitly required, penetration testing is a recommended control under ISO 27001’s Annex A.12 and A.18.

The Benefits of Continuous Pen Testing

While annual pen testing is a good start, cyber threats evolve fast. As we’ve discussed, testing should be conducted more regularly if you’re in an industry that processes sensitive data or at times such as when you have updated systems or migrated to new cloud environments.

Penetration Testing as a Service (PTaaS) offers ongoing testing and reporting so you can be sure that your operations are protected alongside patching and business updates. Benefits include:

Real-time visibility into vulnerabilities
Continuous compliance readiness
Better ROI through faster remediation
Reduced dwell time for threat actors

Conclusion & Next Steps

Penetration Testing is no longer a luxury, it’s your first line of defence in identifying and addressing vulnerabilities before they’re exploited. From compliance to business continuity, it’s essential for protecting your data, your people, and your reputation.

Whether you’re due an annual test or ongoing Penetration testing services, it’s your best chance to stay ahead of threat actors.

Learn more about DigitalXRAID’s penetration testing services. Get in contact to make sure you stay one step ahead of attackers.