<![CDATA[Ubuntu 22.04 LTS Linux servers running default configurations are highly vulnerable to cyber threats including ransomware, cryptojacking, and SSH brute force attacks due to 22+ unnecessary open ports, active root login, and weak password authentication on standard port 22. This research implements systematic hardening through Agile Development methodology comprising 4 iterative phases (assessment, implementation, testing, audit) following CIS Ubuntu Linux Benchmark v2.0.0 guidelines. Results demonstrate Lynis security score improvement from 40/100 (medium risk) to 85/100 (good) representing +112.5% enhancement, 86.4% attack surface reduction (22→3 essential ports: SSH 2222, HTTP 80, HTTPS 443), and complete elimination of critical vulnerabilities. Brute force testing using Hydra (1000 attempts) achieved 95% mitigation within <30 seconds through Fail2Ban automated IP blocking via iptables rules. Defense-in-depth architecture comprises UFW default-deny firewall policy, SSH RSA 4096-bit key authentication, AIDE file integrity monitoring, and automated Lynis auditing via cron jobs. The implementation produces production-ready hardened servers with high availability, replicable Standard Operating Procedures (SOP), and addresses Indonesian cybersecurity research literature gaps.]]>
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