Introduction
Your organisation has just completed a penetration test, and the results aren’t pretty. Critical vulnerabilities everywhere. Your IT team jumps into action mode, patching systems and reconfiguring firewalls like they’re defusing a bomb. Three weeks later, they dust off their hands with satisfaction. “All sorted, boss.”
But here’s the million-pound question: how do you actually know those fixes worked?
Spoiler alert: you don’t. And in cybersecurity, assuming your fixes worked is about as reliable as assuming your teenager cleaned their room just because they said they did.
The False Confidence Trap
Here’s the uncomfortable truth: fixing vulnerabilities on paper doesn’t guarantee they’re fixed in practice.
We’ve seen it countless times: organisations implement what they believe are comprehensive fixes, only to discover during a retest that the vulnerability still exists, or worse, that their “fix” has introduced entirely new security issues.
Think of it like home repairs. If you patch a leaky roof, you don’t just assume it worked; you wait for the next heavy rain to see if water still drips through. Cybersecurity vulnerabilities need the same verification approach.
When Retesting Actually Adds Value
Not every situation calls for an immediate retest, and understanding when retesting provides genuine value versus when it’s just an expensive box-ticking exercise is crucial.
Retest when changes have been made: If your team has modified firewall configurations, updated software, or changed system architectures in response to pen test findings, retesting makes perfect sense. You’ve altered your environment, so verification that these changes achieved their intended security improvements is essential.
Don’t retest unchanged environments repeatedly: If your infrastructure hasn’t changed since the last test, retesting the exact same scope will likely yield identical results. A firewall doesn’t “wear out” like car parts. If it was configured correctly last year and nothing has changed, it will still be configured correctly this year.
Similarly, if the issue itself was regarded as a very minor vulnerability, it’s unlikely that immediate retesting will be required.
The Reality of Retesting Resources
Let’s address something that often catches organisations off guard: not all retests are created equal, and the resource requirements can vary dramatically.
Remote retests are straightforward: Attack surface assessments and web application tests can typically be retested relatively quickly since everything is accessible over the internet. These are the types of retests that can often be offered at reduced rates or as value-adds for larger engagements.
Physical retests are complex: If your original test involved device assessments, internal network testing, or on-site work, retesting becomes significantly more resource-intensive. Devices need to be shipped, travel arrangements made, and full testing days scheduled. The logistics alone make these retests more expensive and time-consuming.
Making Retesting Strategic
For organisations operating under compliance requirements like ISO 27001 or PCI DSS, annual penetration testing is often mandatory. Rather than running the same test repeatedly, consider rotating your testing scope year-over-year while using retesting strategically.
For example:
- Year 1: External infrastructure assessment
- Year 2: Web application security test
- Year 3: Internal network assessment
If significant vulnerabilities are found and fixes implemented in any of these areas, that’s when targeted retesting provides maximum value.
The Business Case for Retesting
Beyond the technical benefits, retesting serves a crucial business function. When you’re presenting security posture updates to your board, CISO, or external auditors, being able to demonstrate that identified vulnerabilities have been genuinely resolved (not just marked as “fixed” in a spreadsheet) builds tremendous confidence.
We’ve worked with organisations where the CEO specifically requested to see retest results to understand whether their security investments were actually reducing risk. That’s the kind of assurance retesting provides: concrete evidence that security improvements aren’t just theoretical.
Balancing Budget and Assurance
Not every organisation has unlimited cybersecurity budgets. If retesting resources are constrained, consider supplementing with regular vulnerability scanning between penetration tests. Monthly or quarterly automated scans can catch newly disclosed vulnerabilities and verify that patch management processes are working effectively.
This hybrid approach allows you to focus your retesting budget on areas where significant changes have been made, while maintaining ongoing visibility into your security posture through automated scanning.
Just don’t be tricked into thinking that vulnerability scans can replace your mandatory pentests. While it might seem biased to say so, we’ve written an article explaining exactly why, right here.
Conclusion
Retesting isn’t an optional extra or a revenue grab by testing providers; it’s quality assurance for your cybersecurity investments. Just as you wouldn’t accept a building contractor’s word that repairs are complete without inspection, your cybersecurity fixes deserve verification.
The key is approaching retesting strategically: understand when it adds genuine value, manage expectations clearly, and use it as part of a broader security assurance program rather than a standalone activity.
Your organisation’s security is too important to leave to assumptions. If you’ve made changes based on penetration test findings, retesting isn’t just recommended; it’s essential for determining whether those changes have actually improved your security posture.
Need help developing a strategic approach to penetration testing and retesting for your organisation? Our team can help you maximise the value of your cybersecurity testing budget while ensuring genuine risk reduction. Get in touch to discuss your specific requirements.