How Penetration Testing Actually Works

Pentesting, short for penetration testing, is an authorised, simulated attack on your organisation’s systems, carried out by a security professional using the same techniques a real attacker would, to find exploitable vulnerabilities before someone with genuinely bad intentions does.

How pentesting differs from a vulnerability scan

These two are often confused but they’re not the same thing. A vulnerability scan is largely automated, it checks systems against a database of known issues and flags what it finds, quickly and at relatively low cost. A penetration test goes further, a skilled tester actively tries to exploit what they find, chains weaknesses together the way a real attacker would and looks for issues automated tools simply can’t identify, like flawed business logic or weaknesses that only appear when several small issues are combined. A scan tells you what might be wrong, a pentest tells you what’s actually exploitable.

The types of pentesting

Penetration testing covers several distinct areas, and which ones matter depends on your organisation’s systems. Network pentesting examines your internal or external network infrastructure for exploitable weaknesses. Web application testing looks specifically at custom-built websites and applications, often where the most organisation-specific vulnerabilities sit. Testing can also extend to wireless networks, cloud environments and even physical or social engineering scenarios, depending on scope. A good testing provider will help you scope the right combination for your actual risk, rather than defaulting to a generic package.

How a pentest actually runs

A typical engagement starts with agreeing scope, exactly which systems are in play and what’s explicitly out of bounds, since testing without clear boundaries carries real risk to live systems. The tester then works through reconnaissance, identifying the attack surface, active testing, attempting to exploit what they find, and reporting, a detailed account of what was found, how it was exploited, and how serious each issue actually is, not just a raw list of findings. The report should prioritise issues by real-world risk, so you know what needs fixing first.

Why pentesting matters beyond ticking a box

It’s tempting to treat pentesting as something done purely to satisfy a client requirement or an insurance condition, and it often is required for exactly those reasons. But the underlying value is real, independent, expert verification that the controls you believe are in place are actually working, tested the way a genuine attacker would test them rather than assumed to be effective because they were configured correctly on paper.

Questions organisations usually ask about pentesting

Will a pentest disrupt our live systems? Scope and timing are agreed in advance specifically to manage this, testing can be scheduled outside business hours, restricted to non-production environments where appropriate, and any potentially disruptive technique is discussed with you before it’s attempted, not sprung on you mid-test.

What’s the difference between a pentest and a red team exercise? A pentest works against an agreed, defined scope over a set time. A red team exercise is broader and more adversarial, simulating a real attacker’s full approach, often without your internal security team knowing it’s happening, to test detection and response as well as raw vulnerability. Most organisations start with pentesting and consider red teaming once their basics are already solid.

Do we need a pentest if we already run vulnerability scans regularly? Scanning and testing serve different purposes, and most well-run security programmes use both, scanning as a frequent, automated check, and pentesting periodically for the deeper, human-led assessment that a scan genuinely can’t replicate.

What happens after the report lands, do you help fix what’s found? A pentest report should give you enough detail to remediate the issues found, prioritised by real risk, and many providers offer follow-up retesting once fixes are in place to confirm the issue is genuinely closed, not just addressed on paper.

How often you should test

There’s no single universal answer, but common triggers include a set annual or biannual schedule, any significant change to your systems, a new application, a major infrastructure change, before a security-conscious client or partner requires evidence, and after any security incident, to confirm the underlying issue is genuinely resolved rather than just patched on the surface. Systems and threats both change continuously, so a test from two years ago tells you very little about your risk today.

If you want to know where your organisation’s systems would actually give way under real attack, our Penetration Testing service is built to find out properly.