The document discusses several steps to harden the security of a Linux server: 1. Create a firewall script to block unwanted traffic and allow only necessary ports like HTTP, HTTPS, SSH. This script is configured as an init script to run at startup. 2. Modify the SSH configuration to change the port from 22 to a non-standard high port, disable root login, and allow only a single restricted user for SSH access. 3. Install Fail2ban and DDoS Deflate tools to prevent brute force attacks and denial of service attempts by automatically blocking offending IP addresses.