Most businesses discover their security vulnerabilities one of two ways: a penetration test, or a breach. One costs a few thousand pounds and a few days of disruption. The other costs an average of $4.45 million globally according to IBM's 2024 Cost of a Data Breach Report.
Here's everything you need to know about penetration testing — what it is, what it covers, who needs it, and what to expect from the process.
What is a penetration test?
A penetration test (or 'pen test') is a simulated cyberattack on your systems, carried out by security professionals with your permission. The goal is to find exploitable vulnerabilities before real attackers do.
A pen tester uses the same techniques a malicious hacker would use — but instead of stealing data or disrupting your systems, they document every vulnerability they find and give you a prioritised remediation report.
What does a penetration test cover?
Network penetration testing
Tests the security of your internal and external network infrastructure — firewalls, routers, servers, and services exposed to the internet. This is the most common type of pen test.
Web application testing
Tests your web applications for vulnerabilities like SQL injection, cross-site scripting (XSS), broken authentication, and insecure direct object references. Critical for any business with a customer-facing web application.
Social engineering
Tests your employees' susceptibility to phishing attacks and other manipulation techniques. Findings are often sobering — humans remain the most exploitable attack surface in most organisations.
Physical security testing
Attempts to gain physical access to your premises, server rooms, or sensitive areas. Less common but important for organisations handling sensitive data on-site.
Who needs a penetration test?
The short answer: any business that holds customer data, processes payments, or relies on digital systems to operate.
You almost certainly need a pen test if: you process credit card payments (PCI-DSS compliance may require it), you handle personal data under GDPR or similar regulations, you're in financial services, healthcare, or legal, you've had a security incident before, or you're about to raise funding and investors are asking about security posture.
What does a penetration test cost?
For a small-to-medium business, a comprehensive penetration test typically ranges from £3,000 to £15,000 depending on scope, complexity, and the depth of testing required. Enterprise-scale testing for large infrastructure can run significantly higher.
The cost seems significant until you compare it to the average cost of a breach ($4.45m), the reputational damage from customer data exposure, or the regulatory fines under GDPR (up to 4% of global annual turnover).
What happens after a pen test?
A good pen test delivers two things: a technical report detailing every vulnerability found, its severity, and how it was exploited; and an executive summary that translates the findings into business risk language for non-technical stakeholders.
Remediation — actually fixing the vulnerabilities — is a separate engagement. Some pen test firms offer this as a bundled service; others deliver findings and leave implementation to your team or a third party.
How to choose a pen testing provider
Look for certifications: CREST, CHECK, or OSCP are the main quality indicators. Ask to see a sample report before engaging — the quality and clarity of reporting varies enormously. Check whether the team has experience in your industry, as sector-specific knowledge matters for understanding which vulnerabilities are most critical.
If you're unsure whether a pen test is the right next step for your business, we offer a free security consultation where we assess your current posture and recommend the most appropriate next steps.