Changing the Default SSH Port (Linux / Ubuntu / Debian)

SSH is one of the most commonly attacked services as it provides easy access to full control of a dedicated server. Changing the default SSH port will help prevent an attacker from launching brute force attacks on the default port.

Step 1

Log in as the server as root (or gain root access by executing sudo su)

Step 2

Check to see the status of the firewall by executing ufw status
If the firewall is active, then we need to add a rule to allow connections for our new SSH port.
This can be done by executing ufw allow newportnumberhere/tcp

Step 3

Execute nano /etc/ssh/sshd_config and look for the line that contains Port 22

Step 4

Change the number 22 to any unused port you’d like

Save and exit by holding down Ctrl and X

Step 5

Restart the SSH service by executing restart ssh within the command line

For Debian, execute service ssh restart

Step 6

If you can still access the command line, type ss -tnlp | grep ssh to verify SSH is listening on the new port. (optional)

Step 7

Start a new SSH session on the new port.

Step 8

Delete the old firewall rule for the old port by executing ufw delete allow 22/tcp