Understanding Automated Scans and the Difference with Manual Security Assessments

In the realm of cybersecurity, automated vulnerability scans are essential tools used to identify potential weaknesses in systems and networks. However, many clients may notice a significant discrepancy between automated scan results and manual assessment reports. Automated scans often flag numerous vulnerabilities that may not pose a real threat, while manual assessments tend to provide a more refined, realistic list of actionable issues.

This article will explain why automated scans often report more vulnerabilities than manual assessments and why both approaches are necessary for a robust cybersecurity strategy.

1. How Automated Vulnerability Scans Work

Automated vulnerability scanners, such as Nessus, Qualys, and OpenVAS, are designed to quickly analyse systems for known weaknesses. These tools use large databases of vulnerabilities and predefined rules to detect potential issues across a wide range of assets.

How the process works:

• The scanner probes systems, looking for version numbers, configurations, open ports, services, and protocols.

• It compares the findings against a vulnerability database to identify known risks.

• A report is generated, listing all potential vulnerabilities and categorising them by severity (e.g., low, medium, high, critical).

While automated scans are fast and comprehensive, they often overestimate the risk by flagging vulnerabilities based on theoretical scenarios rather than contextual factors.

2. Why Automated Scans May Over-Report Vulnerabilities

There are several reasons why automated scans include vulnerabilities that may not be actual threats:

1. False Positives:
Automated scans sometimes flag issues that are not vulnerabilities at all. For example, a scanner may detect an outdated service version but fail to recognise that the vulnerable feature has been disabled or patched manually.

Example:
The scanner might report that an older version of OpenSSH is running, even if the vulnerable cipher suites have already been disabled in the configuration.

2. Lack of Contextual Awareness:
Automated scanners cannot account for environmental or business-specific factors. A vulnerability might not be exploitable in a particular setup due to network segmentation, firewalls, or restricted user access.

Example:
An internal system accessible only to trusted users may be flagged for vulnerabilities that would only pose a risk if the system were exposed to the internet.

3. Configuration Anomalies:
Sometimes, scanners misinterpret benign configurations as potential security risks. This often occurs when tools fail to differentiate between intentional configurations and misconfigurations.

4. Outdated or Inaccurate Vulnerability Signatures:
Scanners rely on signature databases to detect vulnerabilities. If these signatures are outdated or incorrect, the tool may report issues that have already been addressed.

5. Overly Conservative Detection Rules:
Some scanners take a "better safe than sorry" approach, flagging anything that could potentially be risky, even if the likelihood of exploitation is minimal. This is particularly common with low-severity findings.

3. How Manual Security Assessments Provide More Accurate Results

Manual security assessments, such as penetration testing, are conducted by experienced security professionals who apply contextual knowledge and testing techniques to validate vulnerabilities. This process helps reduce false positives and ensures that only real, actionable threats are reported.

Here’s how manual assessments differ from automated scans:

1. Validation of Findings:
Security experts manually verify vulnerabilities identified by automated tools. They attempt to exploit the issue to confirm whether it is a genuine threat. False positives are discarded, leaving only confirmed risks.

2. Contextual Analysis:
Manual assessments consider the business context, system architecture, and security controls in place. This enables testers to determine whether a vulnerability is exploitable in the current environment.

Example:
A vulnerability requiring public access may not be considered a risk if the system is isolated within a secure internal network.

3. Realistic Exploitation Scenarios:
Testers use techniques that mimic real-world attack scenarios to assess the true impact of vulnerabilities. They identify potential attack chains, pivot points, and escalation paths that automated tools might miss.

4. Custom Recommendations:
Based on their findings, security experts provide tailored remediation advice, focusing on high-priority risks. Automated reports, in contrast, often provide generic recommendations that may not apply to the specific environment.

4. Balancing Automated and Manual Assessments

Both automated scans and manual security assessments are critical components of a comprehensive vulnerability management programme. While automated tools are efficient at detecting large numbers of potential vulnerabilities, manual assessments provide a deeper and more accurate understanding of the risks.

Benefits of Automated Scans:

• Fast and scalable.

• Useful for regularly scheduled scans.

• Can quickly identify common vulnerabilities across multiple systems.

Benefits of Manual Assessments:

• Provide context-aware risk analysis.

• Validate vulnerabilities to eliminate false positives.

• Offer realistic exploitation scenarios and tailored mitigation strategies.

By combining these approaches, organisations can maintain an up-to-date view of their security posture while focusing resources on mitigating genuine threats.

5. Example Scenario: Automated vs Manual Assessment

Consider the following scenario:

Automated Scan Result:
The scanner reports a high-severity vulnerability on an application server due to an outdated version of Apache. However, after manual assessment, the tester finds that the specific exploit path for this vulnerability is disabled by custom configuration.

Manual Assessment Result:
The security expert confirms that the outdated Apache version is not a risk due to the hardened configuration. The vulnerability is downgraded to "informational" in the final report, with a recommendation to update the software during the next maintenance cycle.

This scenario demonstrates how manual assessments provide clarity on risk levels that automated scans cannot achieve on their own.

6. Best Practices for Vulnerability Management

To maximise the effectiveness of both automated and manual assessments, organisations should follow these best practices:

1. Regularly Schedule Automated Scans:
Conduct routine scans to maintain visibility into potential vulnerabilities. Use automation to cover a broad range of assets and reduce the burden on security teams.

2. Validate Critical Findings with Manual Assessment:
For high-severity vulnerabilities flagged by automated tools, conduct a manual review to confirm the threat and determine the appropriate response.

3. Prioritise Based on Business Impact:
Focus on vulnerabilities that pose the greatest risk to business operations and sensitive data. Implement risk-based prioritisation rather than addressing issues based solely on scanner severity ratings.

4. Integrate with Security Operations:
Feed automated scan results into your Security Information and Event Management (SIEM) system to enhance monitoring and incident detection.

5. Maintain a Vulnerability Management Policy:
Establish a formal policy that defines roles, responsibilities, and procedures for vulnerability scanning, assessment, and remediation.

7. Conclusion

While automated vulnerability scans are invaluable for quickly identifying potential risks, they often produce false positives and fail to account for context. Manual security assessments complement these scans by validating findings, eliminating false positives, and providing targeted mitigation strategies. By leveraging both approaches, organisations can build a robust defence against cyber threats, focusing their efforts where it matters most.

If you have further questions about vulnerability management or would like to schedule a security assessment, please contact our support team.