How to limit SSH (TCP port 22) connections with ufw on Ubuntu Linux

You can limit SSH (TCP port 22) connections with ufw (Uncomplicated Firewall) on Ubuntu Linux by following these steps:

1. Install ufw if it's not already installed:

sudo apt-get install ufw

1. Enable ufw:

sudo ufw enable

1. Allow incoming SSH connections:

sudo ufw allow 22/tcp

1. Limit the rate of incoming SSH connections:

sudo ufw limit 22/tcp

This will limit the rate of incoming SSH connections to 20 connections per minute by default.

1. Verify the ufw rules:

sudo ufw status numbered

This will show you the rules that have been added to ufw, with the number of each rule.

Note: If you need to make further changes to the ufw rules, you can use the sudo ufw delete <rule number> command to delete an existing rule and sudo ufw insert <position> <rule> command to insert a new rule at a specific position.

These steps will limit the rate of incoming SSH connections to 20 connections per minute, protecting your server from SSH-based brute force attacks.