Penetration testing is a controlled, authorised simulation of a cyber attack against a business's systems, carried out by a skilled tester to identify exploitable vulnerabilities before a real attacker does. Unlike automated vulnerability scanning, a penetration test actively attempts to exploit weaknesses and demonstrate their real-world impact, giving a more accurate picture of genuine risk. It complements baseline controls such as Cyber Essentials by testing custom systems, applications and network configurations in greater depth than a certification self-assessment covers.
How a penetration testing engagement typically runs
A penetration test usually begins with scoping, agreeing exactly which systems will be tested and the boundaries of what the tester is authorised to attempt, followed by reconnaissance, active testing where the tester attempts to identify and exploit vulnerabilities, and a detailed report setting out findings ranked by severity along with remediation recommendations. For businesses running Microsoft 365 and Business Central environments, testing typically focuses on internet-facing infrastructure, remote access configurations, and any custom-built applications or integrations, since these represent the areas most likely to contain exploitable weaknesses beyond what standard Microsoft security controls already cover.
Penetration testing in practice
- A business commissions an annual external penetration test to satisfy a customer's supplier security questionnaire, providing independent evidence of its security posture.
- An organisation launching a new customer-facing web portal commissions a web application penetration test before go-live, identifying and fixing vulnerabilities before they are exposed to real users.
- A finance business pursuing cyber insurance uses penetration test results to demonstrate active, ongoing security testing as part of its insurance application.
- An IT team uses penetration test findings to prioritise a remediation backlog, focusing first on the highest-severity exploitable vulnerabilities rather than addressing issues in an arbitrary order.
How Advantage supports penetration testing for clients
Advantage coordinates penetration testing engagements as part of a wider managed IT and cyber security service, scoping tests appropriately to a business's infrastructure and helping translate findings into a prioritised remediation plan. We help businesses use penetration testing alongside Cyber Essentials, multi-factor authentication and ongoing security monitoring as part of a layered approach to security rather than a one-off compliance exercise.
Frequently Asked Questions
Common questions about penetration testing for UK businesses.
How is penetration testing different from a vulnerability scan?
A vulnerability scan is an automated process that identifies known weaknesses, such as missing patches or misconfigured settings, across a system or network. Penetration testing goes further, with a skilled tester actively attempting to exploit identified weaknesses, chain them together, and demonstrate the real-world impact of a successful attack, such as gaining access to sensitive data. Vulnerability scanning is typically faster and cheaper, while penetration testing gives a more realistic picture of actual exploitable risk.
What types of penetration testing are most relevant to an SME?
The most common types relevant to SMEs are external penetration testing, assessing internet-facing systems such as websites and remote access points for vulnerabilities an outside attacker could exploit; internal penetration testing, simulating what an attacker could do if they gained access to the internal network; and web application testing, focused specifically on custom-built applications or portals. Most SMEs start with external testing, since internet-facing systems represent the most immediate exposure to opportunistic attackers.
How often should a business carry out penetration testing?
Annual penetration testing is common practice for businesses handling sensitive data or required to demonstrate ongoing security assurance to customers or insurers, with additional testing recommended after any significant change to infrastructure, such as a new public-facing application or a major network change. Cyber Essentials Plus certification involves its own technical verification, but does not replace the depth of a dedicated penetration test against custom systems and applications.
