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Server Security Testing: A Practical Guide

G5 Cyber Security

TL;DR

Regularly test your servers for security weaknesses using automated tools and manual checks. This guide covers key areas like vulnerability scanning, configuration reviews, penetration testing, and log analysis to help you find and fix problems before attackers do.

1. Vulnerability Scanning

Vulnerability scanners automatically check your server for known software flaws. They’re a good first step but don’t catch everything.

  1. Choose a Scanner: Popular options include Nessus, OpenVAS (free), and Qualys. Consider both commercial and open-source tools.
  2. Configure the Scan: Specify your server’s IP address or hostname. Define scan profiles to focus on specific types of vulnerabilities (e.g., web application, operating system).
  3. Run the Scan: Schedule regular scans – weekly is a good starting point.
  4. Review Results: Prioritise findings based on severity. High-severity vulnerabilities need immediate attention.

Example Nessus command (from the CLI):

nessuscli scan -t 'Basic Network Scan' 192.168.1.10

2. Configuration Reviews

Incorrect server configurations are a common source of security problems. Automated tools can help identify misconfigurations.

  1. Use a Configuration Management Tool: Tools like Ansible, Chef, or Puppet enforce consistent settings.
  2. Implement CIS Benchmarks: The Center for Internet Security (CIS) provides detailed security configuration guidelines for various operating systems and applications. CIS Benchmarks.
  3. Automate Checks: Use tools like Lynis or scripts to regularly check against CIS benchmarks.

Example using Lynis (from the command line):

lynis audit system

3. Penetration Testing

Penetration testing simulates a real-world attack to identify vulnerabilities that automated scans might miss.

  1. Choose a Tester: Hire a reputable penetration testing company or use an in-house team with appropriate skills.
  2. Define Scope: Clearly define what systems are included in the test and any limitations (e.g., no denial-of-service attacks).
  3. Black Box, Grey Box, White Box: Decide on the testing approach:
    • Black Box: Tester has no prior knowledge of the system.
    • Grey Box: Tester has some limited knowledge (e.g., network diagram).
    • White Box: Tester has full access to source code and documentation.
  4. Review Report: Carefully review the penetration testing report and address all identified vulnerabilities.

4. Log Analysis

Regularly analysing server logs can help detect suspicious activity.

  1. Centralised Logging: Collect logs from all servers in a central location (e.g., using ELK Stack, Splunk).
  2. Implement SIEM: A Security Information and Event Management (SIEM) system can automate log analysis and alert you to potential threats.
  3. Look for Anomalies: Monitor logs for unusual patterns, failed login attempts, and other suspicious events.

Example using `grep` to find failed SSH login attempts:

grep 'Failed password' /var/log/auth.log

5. Web Application Security Testing

If your server hosts web applications, specific testing is needed.

  1. Static Application Security Testing (SAST): Analyse source code for vulnerabilities before deployment.
  2. Dynamic Application Security Testing (DAST): Test the running application for vulnerabilities (e.g., using OWASP ZAP).
  3. OWASP Top 10: Focus on the most common web application security risks identified by the Open Web Application Security Project (OWASP). OWASP Top Ten.

6. Automation

Automate as much of the security testing process as possible.

  1. CI/CD Integration: Integrate vulnerability scanning and SAST into your Continuous Integration/Continuous Delivery pipeline.
  2. Scheduled Scans: Schedule regular vulnerability scans and configuration reviews.
  3. Alerting: Set up alerts to notify you of critical vulnerabilities or suspicious activity.
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