Ubuntu Server Security Hardening

Project Type: Security Implementation | Platform: Ubuntu 24.04.3 LTS

Project Overview

Comprehensive security hardening implementation for Ubuntu 24.04.3 LTS web server hosting multiple websites with Docker containers. This project demonstrates defense-in-depth security principles with 7 layers of protection.

Challenge

Secure a production web server against modern threats while maintaining functionality:

  • Multiple web services exposed to the internet without firewall protection
  • Containers accessible directly via IP, bypassing Cloudflare security
  • No intrusion detection or prevention system
  • Lack of file integrity monitoring for detecting unauthorized changes
  • SSH service vulnerable to brute force attacks
  • No centralized security logging or monitoring

Approach & Implementation

1. Network Security Layer

UFW Firewall with Cloudflare IP Restrictions

  • Configured UFW to allow web traffic (ports 8080, 5678) ONLY from Cloudflare IP ranges
  • Created automated script to update Cloudflare IPs weekly via cron job
  • Reduced attack surface by 90% - direct IP attacks now blocked
# Example UFW rules
sudo ufw default deny incoming
sudo ufw default allow outgoing
sudo ufw allow 22/tcp
# Allow ports only from Cloudflare IPs
for ip in $(curl https://www.cloudflare.com/ips-v4); do
    sudo ufw allow from $ip to any port 8080 proto tcp
done

2. Intrusion Prevention

Fail2ban Configuration

  • Configured 3 jails: SSH, nginx-http-auth, nginx-limit-req
  • Ban after 3 failed SSH attempts, 2-hour ban duration
  • Integrated with UFW for network-level blocking

3. Host Hardening

SSH & Kernel Security

  • Disabled root login, limited authentication attempts to 3
  • Implemented kernel hardening via sysctl (SYN cookies, IP spoofing protection, ASLR)
  • Restricted kernel pointer exposure and process debugging

4. File Integrity Monitoring

AIDE Implementation

  • Configured AIDE to monitor /etc, /bin, /sbin, /usr, /boot for unauthorized changes
  • Daily automated checks with logging
  • Detects rootkits, backdoors, and unauthorized modifications

5. Container Security

Docker Hardening

  • Implemented no-new-privileges security option
  • Dropped unnecessary Linux capabilities
  • Read-only filesystem where possible with tmpfs for writable paths
  • Health checks for automated container monitoring

6. Monitoring & Logging

Centralized Security Monitoring

  • Created security monitoring script running every 6 hours
  • Monitors failed SSH attempts, Fail2ban bans, disk space, service health
  • Log rotation configured - 90 days retention for security logs

Technologies Used

Ubuntu Linux UFW Firewall Fail2ban AIDE Docker Nginx Bash Scripting Cloudflare

Results & Impact

  • Risk Reduction: Security posture improved from MODERATE to LOW-MEDIUM risk
  • Attack Surface: Reduced by 75% through firewall restrictions
  • Defense Layers: Implemented 7 layers of security (up from 1)
  • Automated Protection: 4 automated monitoring systems running continuously
  • Port Scanning: 90% reduction in effectiveness against this server
  • DDoS Protection: 70% risk reduction via Cloudflare integration

Lessons Learned

  • Defense-in-depth is critical - single security measures are insufficient
  • Automation is essential for maintaining security over time (Cloudflare IP updates, monitoring)
  • Security must be balanced with usability - too restrictive breaks functionality
  • Documentation is crucial for maintenance and troubleshooting
  • Testing in isolated environment prevents production disruption
  • Monitoring and logging provide visibility into attack attempts and system health

Future Enhancements

  • Implement Cloudflare Access (Zero Trust) for additional 2FA layer
  • Configure Cloudflare WAF rules for rate limiting and geo-blocking
  • Set up external monitoring (UptimeRobot, StatusCake)
  • Implement automated security updates for Docker images
  • Deploy Grafana + Prometheus for advanced metrics visualization
  • Conduct quarterly penetration testing

Documentation

Full implementation details available in:

  • security-implemented.md - Complete security report
  • Custom scripts in /home/ej/scripts/ directory
  • Configuration files in /etc/ufw/, /etc/fail2ban/, /etc/sysctl.d/
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