Certified: The Security+ Prepcast

Remediation is not complete until you prove that it worked. You may have applied a patch, updated a configuration, or implemented a compensating control—but how do you know the vulnerability is truly resolved? The final step in the vulnerability management lifecycle is validation. This is where you confirm that your efforts were successful, and that the risk has been reduced or eliminated. In this episode, we look at two essential components of that final step: rescanning and verification, followed by audit and continuous validation.
Let’s begin with rescanning and verification. After applying a fix, one of the first actions you should take is to run another scan. This rescanning process confirms whether the vulnerability still appears in the environment and whether the patch or remediation measure was applied correctly. It also ensures that nothing was missed or misconfigured in the response.
Rescanning is more than a simple formality. Vulnerabilities can remain present even after an attempted fix due to several common issues. The patch may not have installed correctly. The fix may have required a reboot that was never completed. Or, in some cases, the wrong patch may have been applied altogether. Rescanning helps detect these gaps and gives the security team a chance to intervene before an attacker finds the same vulnerability still active.
To be effective, rescanning should be targeted and timely. Targeted, meaning it should focus on the systems where remediation took place, and timely, meaning it should occur soon after the change. This reduces the window of uncertainty and allows you to catch issues before the next round of vulnerability discovery or audits. If possible, use the same scanning tools as before, to maintain consistency in the detection methodology and results.
Beyond rescanning, verification includes additional techniques to confirm that the vulnerability is no longer exploitable. For example, a penetration tester may reattempt the original exploit. If access is denied or the behavior has changed, that is a sign that the fix worked. Administrators may also manually inspect configurations or logs to confirm that settings have changed, services have been disabled, or access rules have been updated.
Verification is particularly important in environments where compensating controls were used instead of direct patching. In these cases, security teams must validate that the controls are active, functioning, and reducing risk as expected. For example, if a firewall rule was added to block a vulnerable port, administrators should test whether traffic to that port is actually being denied. If a log monitoring tool was put in place, the team should confirm that alerts are being triggered and acted upon.
Let’s consider a real-world example. A city government identifies a cross-site scripting vulnerability in its citizen portal. The development team applies a fix to sanitize user input. After deployment, the security team runs a new scan and verifies that the vulnerability no longer appears in the report. But they do not stop there. They also perform a manual test by submitting the same input string that originally triggered the flaw. This time, the input is blocked. Logs show the detection and handling of the attempt. This multi-layered verification confirms that the vulnerability is resolved, and the portal is now more secure.
Another example involves a cloud-based storage system. A scanner reports that anonymous access is enabled on a storage bucket. The cloud administrator updates permissions to require authentication and limits access to specific roles. A follow-up scan confirms the change, and access attempts from non-authorized accounts fail. The remediation has been verified, and the risk has been closed.
Verification should be documented. This includes the date of the fix, the results of the rescan, and any manual checks that were performed. Documentation provides accountability and supports audit readiness. It also helps the organization learn from each vulnerability and refine its remediation processes for the future.
That brings us to our second topic: audit and continuous verification. While rescanning is often event-driven—performed after a specific fix—continuous verification is part of an ongoing, proactive security program. It includes regular audits, monitoring, and automated checks to ensure that vulnerabilities remain resolved and that security posture is improving over time.
Auditing involves reviewing systems, configurations, and processes on a recurring schedule. This may include revisiting previously remediated vulnerabilities to ensure they have not reappeared. It may also include validating that patch levels remain current, that configurations remain hardened, and that new vulnerabilities are not being introduced through system changes or updates.
Continuous verification often relies on automation. Security tools can perform daily or weekly scans, flag configuration drift, and alert administrators when risk levels change. For example, if a previously secured system reverts to a default configuration or a patch is removed during a rollback, automated tools can detect this and trigger a response. This helps maintain a strong security baseline and reduces reliance on manual reviews.
Monitoring tools can also help with behavioral verification. If a vulnerability previously led to suspicious activity—such as repeated login attempts, malformed input, or unexpected outbound traffic—security teams can set alerts to watch for the same patterns. The absence of such behavior after remediation is another indicator that the fix was successful. Conversely, if those patterns persist, it may suggest the fix was incomplete or bypassed.
Let’s examine how this plays out in a practical setting. A financial firm integrates continuous scanning and configuration monitoring into its vulnerability management program. After resolving a critical remote access vulnerability, the team sets up alerts for changes to firewall rules and login activity from untrusted networks. Three months later, a system administrator accidentally reopens a vulnerable port during a configuration change. The monitoring system catches the change, and the security team responds immediately. This level of visibility and responsiveness is only possible with continuous verification in place.
Another organization uses a centralized dashboard to track remediation metrics. It monitors how long vulnerabilities remain open, how often rescans are performed, and how many issues reappear over time. This data helps identify trends, gaps in process, or recurring misconfigurations. It also gives leadership a clear picture of how well the organization is managing its vulnerabilities—and where to invest in improvement.
Continuous verification also supports compliance. Many regulatory frameworks require evidence that vulnerabilities are not only detected and remediated, but also verified and monitored on an ongoing basis. For example, the Payment Card Industry Data Security Standard expects organizations to track the status of vulnerabilities through to resolution and confirm that fixes are applied correctly. Without documentation and follow-up, compliance becomes difficult to demonstrate.
To summarize, validating remediation efforts is the final, crucial step in the vulnerability management lifecycle. Rescanning confirms that technical fixes have been applied, while verification ensures that the risk has actually been mitigated. These steps include both automated scans and manual tests, depending on the environment and the nature of the vulnerability. Continuous verification—through monitoring, audits, and automation—helps maintain long-term security and supports ongoing improvement. Together, these practices close the loop and ensure that vulnerabilities are not just addressed, but truly resolved.
For the Security Plus exam, be ready to explain the importance of rescanning, identify the purpose of manual verification, and describe how continuous monitoring supports remediation. Expect scenario questions involving configuration drift, audit findings, or recurring vulnerabilities. Be familiar with terms like validation, drift detection, remediation tracking, and compensating control testing—they often appear in performance-based and multiple-choice questions.