Penetration testing — often called pen testing — is a controlled cyber attack against your own systems, performed by security professionals to find vulnerabilities before real attackers do. Think of it as hiring a locksmith to try breaking into your house so you can fix the weak spots.
How Penetration Testing Works
A penetration test follows a structured methodology. The tester begins with reconnaissance — gathering information about your network, applications, and infrastructure. Next comes scanning, where automated tools identify open ports, services, and potential entry points. The exploitation phase is where the tester attempts to breach your defences using the discovered vulnerabilities. Finally, a detailed report documents every finding with severity ratings and remediation steps.
Types of Penetration Testing
Network penetration testing examines your external and internal network infrastructure — firewalls, routers, servers, and endpoints. Web application testing focuses on your websites and web apps, looking for SQL injection, cross-site scripting (XSS), authentication flaws, and business logic errors. Mobile application testing covers Android and iOS apps. Social engineering tests evaluate your human defences through phishing simulations and pretexting.
Black Box vs White Box vs Grey Box
In a black box test, the tester has zero prior knowledge of your systems — simulating an external attacker. White box testing gives the tester full access to source code, architecture diagrams, and credentials — maximising coverage. Grey box testing falls in between, providing partial information like user-level credentials to simulate an insider threat or compromised employee account.
Why Your Business Needs Regular Pen Tests
Compliance frameworks like PCI DSS, ISO 27001, and SOC 2 require periodic penetration testing. Beyond compliance, pen tests reveal real-world risks that vulnerability scanners miss. Automated tools find known CVEs, but a skilled tester chains multiple low-severity issues into a critical breach path. A single unpatched service combined with weak credentials and missing network segmentation can give an attacker domain admin access in hours.
How Often Should You Test?
At minimum, conduct a penetration test annually. High-risk environments — financial services, healthcare, e-commerce — should test quarterly. You should also retest after major infrastructure changes, new application deployments, or significant code updates. Continuous penetration testing platforms are emerging as an alternative for organisations with frequent releases.
Choosing a Penetration Testing Provider
Look for certified professionals — OSCP, CREST, or CEH credentials indicate hands-on skills. Ask for sample reports to evaluate their reporting quality. Ensure they follow responsible disclosure practices and carry professional indemnity insurance. A good pen test report should not just list vulnerabilities — it should provide clear, prioritised remediation guidance your team can act on.
What Happens After the Test
The real value of a pen test is in the remediation. Prioritise critical and high findings for immediate patching. Medium findings should have a 30-day remediation window. Schedule a retest to verify that fixes actually work. Use findings to update your security policies, employee training, and incident response procedures.
