docs(bot): 📝 Add SSH security guide to README.

README.md

@@ -112,6 +112,72 @@ You'll get a command to paste in your new node. Copy the one that ends with `--w
 in your new node. Wait a few minutes until it connects, and then you're ready to go! No need to
 follow the steps down below if the cluster is already up and running.
 
+##### SSH Security
+
+To secure the access to the server, you'll need to follow the following steps:
+
+###### Disable Password Authentication
+
+Having SSH password authentication leaves an open door for brute force attacks. Before disabling
+it, make sure that the server has your SSH key to prevent from getting locked out after proceeding.
+
+After you have made sure your keys have been properly configured, edit the SSH configuration file:
+
+```sh
+nano /etc/ssh/ssh_config
+```
+
+In the file, find the following configurations:
+1. `ChallengeResponseAuthentication`
+2. `PasswordAuthentication`
+3. `UsePAM`
+
+If they're set in the file, set their value to `no`. After that, restart the SSH service:
+
+```sh
+systemctl restart ssh
+```
+
+###### Set Up `fail2ban`
+
+The next step to secure SSH is to set up `fail2ban`, which will rate limit failed attempts to log
+in. First, install it in the server:
+
+```sh
+apt update
+apt install fail2ban
+```
+
+Next, make a copy of the configuration file:
+
+```sh
+cd /etc/fail2ban
+cp jail.conf jail.local
+```
+
+You now need to update it to enable SSH protection:
+
+```sh
+nano jail.local
+```
+
+Find the `[ssh]` section and add the following line (or update it if it already exists):
+
+```toml
+enable = true
+```
+
+After updating that line, close the file, enable, and start the service:
+
+```sh
+systemctl enable fail2ban
+systemctl start fail2ban
+
+# Check the status of the service to make sure it was enabled properly. You can exit the status
+# screen pressing "q".
+systemctl status fail2ban
+```
+
 ## Deploying Payphone
 
 The following steps show how to pull and install Payphone on a running cluster of nodes.