Penetration testing and vulnerability scanning are both critical to the ongoing security of any organisation, but there remains confusion, even amongst IT professionals, about the difference between them and when each should be used.
In short: vulnerability scanning checks your systems for known vulnerabilities to identify your exposure to risk. Penetration testing goes further and actively attempts to exploit those vulnerabilities, just as a real attacker would. They are different approaches, and most organisations need both.
What is penetration testing?
There are several types of penetration test. Internal and external network tests, web application tests, and API tests all follow the same core principle: an experienced tester uses a combination of tools and manual techniques to discover vulnerabilities and then attempts to exploit them, replicating what a malicious actor would do in a real attack.
External testing assesses infrastructure that is accessible from the internet, typically firewalls, VPNs, and publicly facing services. It evaluates the risk of an attacker identifying those services and exploiting weaknesses in them, while also testing whether employees can be phished for access.
Internal testing is carried out against devices and systems within the organisation's network, simulating what an attacker could do after gaining an initial foothold.
Effective penetration testing requires deep knowledge of infrastructure, systems architecture, and current attacker techniques. Testers stay close to the latest vulnerabilities and exploitation methods, often identifying weaknesses that automated tools miss entirely. A typical engagement takes anywhere from a few days to a few weeks and concludes with detailed reports and prioritised remediation actions.
What is vulnerability scanning?
Vulnerability scanning is the process of identifying known vulnerabilities across network devices, servers, desktops, laptops, and cloud infrastructure. Unlike penetration testing, vulnerability scanning is automated and focuses on detection rather than exploitation. The goal is to find vulnerabilities, not to prove whether they can be exploited.
Because scanning is automated, it is cost-effective to run frequently. Organisations can discover known vulnerabilities and patch them on a regular cycle, reducing the window of exposure. However, scanning alone is not enough. It should be coordinated with penetration testing to provide a comprehensive approach that combines ongoing detection with periodic, in-depth validation.
How often should you test?
We are often asked how regularly vulnerability scanning and penetration testing should be undertaken. The answer depends on several factors: changes to systems or networks, new hardware or software deployments, organisational changes, and any regulatory or compliance requirements.
For example, the Payment Card Industry Data Security Standard (PCI DSS) requires organisations to run internal and external network vulnerability scans at least quarterly and after any significant change to the network.
Industry best practice and most compliance frameworks recommend vulnerability scanning at least quarterly and penetration testing annually. However, as new vulnerabilities are discovered at an increasing rate, organisations that take security seriously should go beyond the minimum. Many of our clients have opted for monthly vulnerability scans and twice-yearly penetration testing. The right frequency for your organisation comes down to how much risk you are prepared to accept, balanced against the cost of regular testing.
Different but equally important
Vulnerability scanning and penetration testing together inform your cyber risk analysis and help determine the controls needed at the business, department, and individual level. The reports from both will typically highlight not just technical weaknesses, but the need for better security awareness among employees, who remain the most commonly exploited link in the chain.
Using security tools without the right expertise can itself create risk. Our CREST-certified team has the deep knowledge required to run these assessments effectively, delivering actionable results that genuinely improve your security posture.
If you want to understand where your organisation's vulnerabilities lie and close the gaps before an attacker finds them, get in touch and we will walk you through the process.