How to remediate – Post-Scan Rules Application

1. Introduction

The Post-Scan Rules Application plugin analyzes scan results and adjusts vulnerabilities based on user defined settings. This is important because it ensures scans accurately reflect an organisation’s security posture, reducing false positives and focusing remediation efforts. Systems commonly affected are those running vulnerability scanners with configurable rule sets. A successful misconfiguration could lead to undetected vulnerabilities, impacting confidentiality, integrity, and availability.

2. Technical Explanation

• Root cause: Incorrectly configured user defined scan rules.
• Exploit mechanism: An attacker exploits vulnerabilities missed due to flawed rules. For example, a rule might suppress alerts for a specific port, allowing an open service to go unnoticed.
• Scope: Vulnerability scanners with configurable post-scan rule application settings.

3. Detection and Assessment

• Quick checks: Check the scanner’s web interface for applied post-scan rules.
• Scanning: No specific signature IDs are available, as this relates to configuration.
• Logs and evidence: Review scanner logs for rule application events. The location varies by scanner product.

# Example command placeholder:
# No direct command is applicable; review the scanner's UI or log files.

4. Solution / Remediation Steps

Fixing this issue requires careful configuration of post-scan rules. Follow these steps to ensure accurate vulnerability reporting.

4.1 Preparation

• Ensure you have access to the scanner’s administrative interface. A roll back plan involves restoring the previous configuration snapshot.
• A change window may be needed depending on scan schedules and criticality. Approval from a security lead is recommended.

4.2 Implementation

1. Step 1: Review each post-scan rule, understanding its purpose and impact.
2. Step 2: Remove any rules that suppress critical vulnerabilities without justification.
3. Step 3: Adjust overly permissive rules to be more specific and targeted.
4. Step 4: Test the changes by running a scan with the updated rules.

4.3 Config or Code Example

Before

Suppress alerts for port 21 (FTP) - all severity levels

After

Remove rule suppressing alerts for port 21. Investigate any FTP services and remediate if necessary.

4.4 Security Practices Relevant to This Vulnerability

List only practices that directly address this vulnerability type. Use neutral wording and examples instead of fixed advice. For example: least privilege, input validation, safe defaults, secure headers, patch cadence. If a practice does not apply, do not include it.

• Practice 1: Least privilege – limit access to scanner configuration to only authorised personnel.
• Practice 2: Regular review – schedule regular reviews of post-scan rules to ensure they remain appropriate and effective.

4.5 Automation (Optional)

# Example PowerShell snippet to export scanner rules:
# Get-ScannerRule -ConfigurationPath "C:ScannerConfig" | Export-Csv -Path "C:RulesExport.csv"
# This requires the appropriate Scanner module to be installed and configured.

5. Verification / Validation

Confirming the fix involves verifying rule changes and re-running scans. Check for expected vulnerability reports.

• Post-fix check: Review the scanner’s web interface to confirm rules have been modified as intended.
• Smoke test: Confirm scans complete successfully without errors and generate reports.
• Monitoring: Monitor scanner logs for unexpected rule application events or changes to configuration.

# Post-fix command and expected output
# No direct command; verify via the scanner's UI that port 21 alerts are no longer suppressed.

6. Preventive Measures and Monitoring

Suggest only measures that are relevant to the vulnerability type. Use “for example” to keep advice conditional, not prescriptive.

• Baselines: Update security baselines to include recommended post-scan rule configurations.
• Pipelines: Integrate scanner configuration reviews into CI/CD pipelines.
• Asset and patch process: Implement a regular review cycle for scanner rules (for example, quarterly).

7. Risks, Side Effects, and Roll Back

• Risk or side effect 2: Incorrectly configured rules may still suppress vulnerabilities; regular review is essential.
• Roll back: Restore the previous configuration snapshot taken in step 4.1.

8. References and Resources

• Vendor advisory or bulletin: Consult your scanner vendor’s documentation for best practice rule configuration.
• NVD or CVE entry: Not applicable, as this is a configuration issue rather than a specific software flaw.
• Product or platform documentation relevant to the fix: Refer to your vulnerability scanner’s official user guide for detailed instructions on managing post-scan rules.