First steps to secure a new Linux server

A server on the internet is scanned by bots within minutes. These few steps protect it against most attacks.

1. Update the system

apt update && apt upgrade -y      # Debian / Ubuntu
dnf upgrade -y                    # AlmaLinux / Rocky

2. Use a strong password, or better an SSH key

Change the password with the command below. With an SSH key you can then turn off password logins completely.

passwd

3. Turn on a firewall

On Ubuntu, allow SSH first and then enable the firewall, so you do not lock yourself out.

ufw allow OpenSSH
ufw enable

4. Block repeated login attempts

apt install -y fail2ban

If you think your server was compromised (very high CPU, unknown processes, spam), reinstall it from your client area and restore only clean data.