By default, ssh listens for incoming connections on port 22. For a hacker to determine ssh is running on your machine, he’ll most likely scan port 22 to determine this.
To make the change, add a line like this to your /etc/ssh/sshd_config file:
vi /etc/ssh/sshd_config
Now change the list Port to anything you choose, except a port that is reserved for known services.
Port 23145 #Change me