Linux security is very complicated. The day my server almost got hacked was the day I learned about firewall settings. Since then I am always careful. I always disable root login, change SSH port, set up fail2ban, and install basic firewalls like UFW. Regular updates are also very important as well.
How do you guys secure your Linux servers
What's the best Practices for Securing a Linux Server
Re: What's the best Practices for Securing a Linux Server
Use strong passwords and SSH keys,these are important steps. You can also try methods like limiting user privileges, configuring firewalls, disabling unnecessary services, enabling SELinux/AppArmor. Also, monitor logs, install security tools, encrypt sensitive data, and maintain regular off-site backups to protect against attacks and failures.