Why vulnerability scanners are indispensable – and why they are no substitute for a penetration test

What is a vulnerability scanner?

A vulnerability scanner is an automated tool that checks networks, systems, servers, applications and end devices for known security vulnerabilities. These scans are essential for effective vulnerability management, as they can be carried out regularly to detect vulnerabilities at an early stage.

How does a vulnerability scanner work?

A vulnerability scanner works according to the following principle:

1. Detection: The tool identifies IT systems and applications in the network.
2. Analysis: It checks these systems for outdated software, incorrect configurations, open ports or insecure passwords.
3. Comparison with vulnerability databases: The scanner compares the information found with known vulnerabilities (e.g. from the CVE database or threat intelligence feeds).
4. Assessment: Each vulnerability discovered is assessed with a severity level (e.g. CVSS score).
5. Report and recommendations for action: Companies receive a detailed report with a prioritisation of the vulnerabilities found as well as recommendations for remediation.

Advantages of vulnerability scanners

✔ Automated detection: Fast and efficient, even in large IT environments.
✔ Regular security tests: Companies can scan at short intervals to identify new vulnerabilities at an early stage.
✔ Compliance & audits: Many legal requirements (e.g. GDPR, ISO 27001, PCI-DSS) require regular vulnerability analyses.
✔ Cost-efficient: Significantly cheaper than manual security tests.

Why a vulnerability scanner is no substitute for a penetration test

While a vulnerability scanner automatically searches for known security vulnerabilities, a penetration test (pentest) goes far beyond this. A penetration test is a manual security check by ethical hackers who act like real attackers to penetrate a system.

Main differences between vulnerability scanners and penetration tests

Why is a penetration test so important?

Penetration tests are essential because cyber criminals are not looking for known vulnerabilities, but for every possible point of attack. While a scanner merely reports that outdated software exists, a pentest can show whether it can really be exploited – and how far an attacker can get with it.

A realistic attack simulator not only checks technical vulnerabilities, but also human errors and operational processes. One example:

• A scanner recognises that a web application contains an SQL injection vulnerability.
• A pentester checks whether sensitive customer data can be read out via this – and whether admin rights can be obtained.

The optimal approach: a combination of both

A comprehensive cybersecurity concept should include both vulnerability scans and regular penetration tests.

Vulnerability scanners are the foundation of good vulnerability management. They detect problems at an early stage and enable a rapid response.
🔹 Penetration tests go one step further by simulating real attack scenarios and showing whether a vulnerability can really be exploited.

Best practices for IT security

✅ Carry out regular vulnerability scans: At least monthly to identify new gaps at an early stage.
✅ S chedule pentests 1-2 times a year: Especially after major changes to IT systems or the introduction of new software.
✅ Reduce false positives: A pentest helps to distinguish false positives from genuine threats.
✅ Prioritise vulnerabilities: Not every vulnerability found is critical. A SIEM system or Risk-Based Vulnerability Management (RBVM) helps with prioritisation.

CVE – The central database for known vulnerabilities

The Common Vulnerabilities and Exposures (CVE) database is a globally recognised register for documented security vulnerabilities. Each identified vulnerability is assigned a unique CVE number, which helps companies, IT security managers and developers to systematically record security vulnerabilities and take targeted countermeasures.

The CVE database is managed by the MITRE Corporation and supplemented by the National Vulnerability Database (NVD), which provides detailed evaluations and risk assessments for each vulnerability identified. Organisations use this information to review their IT systems and ensure that critical vulnerabilities are addressed through updates or configuration changes.

How does CVE work in practice?

1. Discovery: A security researcher or a company discovers a new vulnerability in a software or system.
2. Reporting and analysis: The vulnerability is reported to a CVE organisation or the software manufacturer and analysed.
3. Assignment of a CVE number: If the vulnerability is confirmed, it is assigned a unique CVE ID (e.g. CVE-2024-12345).
4. Public announcement: The vulnerability is published in the CVE database, often with additional information on the threat situation.
5. Patch or workaround: The affected manufacturer publishes a patch or an alternative security measure to close the vulnerability.

Why is CVE important for companies?

• Transparency & standardisation: Companies can search specifically for CVEs that affect their software and react more quickly.
• Integration into security solutions: Modern vulnerability scanners, SIEM systems and threat intelligence platforms use the CVE database for automated threat analyses.
• Regulatory requirements: Many compliance requirements (e.g. ISO 27001, GDPR, PCI-DSS) require organisations to regularly identify and fix known vulnerabilities.

Why is patch management so important?

Patch management is the process by which software updates are installed to close known vulnerabilities before they can be exploited by attackers. Without effective patch management, systems remain vulnerable – even if a vulnerability is known.

Why are unpatched systems a risk?

Hackers specifically exploit known vulnerabilities, often shortly after their release. This is known as “Exploit Wednesday” – the day after Patch Tuesday, when major manufacturers such as Microsoft release new updates, attackers analyse the updates and develop exploits for companies that have not yet patched them.

Challenges in patch management

• Testing & compatibility: Companies must ensure that new patches do not cause any undesirable side effects in existing systems.
• Prioritisation: Not every vulnerability is equally critical. A risky privilege escalation exploit on a production server is more dangerous than a DoS vulnerability in a non-exposed environment.
• Legacy systems: Older systems or specialised hardware often no longer have updates. Alternative protective measures are required here, such as network segmentation or virtual patching solutions.

Best practices for effective patch management

✅ Automated patch management: Check systems regularly and automatically for updates.
✅ Prioritisation of security vulnerabilities: Prioritise patching critical CVEs with a high CVSS score.
✅ Use test environments: Test updates in a non-production environment first.
✅ Define fallback strategies: If a patch fails, a rollback option should be available.
✅ Monitoring & reporting: A SIEM or vulnerability scanner can monitor the status of patched and unpatched systems.

Not an either/or, but an interplay

Vulnerability scanners are an essential part of the IT security strategy, as they continuously detect vulnerabilities and thus enable proactive defence. However, they are no substitute for a penetration test that simulates how a real attacker would proceed.

Companies that combine both approaches can significantly increase their cyber resilience and effectively protect themselves against data leaks, ransomware and other attacks.

🔹 Tip for companies: Supplement your regular vulnerabilityscans with targeted penetration tests to improve your IT security holistically.