The Secure Shell (SSH) Protocol by default uses port 22. Accepting this value does not make your system insecure, nor will changing the port provide a significant variance in security. However, changing the default SSH port will stop many automated attacks and a bit harder to guess which port SSH is accessible from. In other words, a little security though obscurity.
Steps to follow
Step 1
As root, use your favorite text editor (vi) to edit the sshd configuration file.
#vi /etc/ssh/sshd_config
Step 2
Edit the line which states ‘Port 22’. But before doing so, you’ll want to read the note below. Choose an appropriate port, also making sure it not currently used on the system.
# What ports, IPs and protocols we listen for
Port 50683
Note: The Internet Assigned Numbers Authority (IANA) is responsible for the global coordination of the DNS Root, IP addressing, and other Internet protocol resources. It is good practice to follow their port assignment guidelines. Having said that, port numbers are divided into three ranges: Well Known Ports, Registered Ports, and Dynamic and/or Private Ports. The Well Known Ports are those from 0 through 1023 and SHOULD NOT be used. Registered Ports are those from 1024 through 49151 should also be avoided too. Dynamic and/or Private Ports are those from 49152 through 65535 and can be used. Though nothing is stopping you from using reserved port numbers, our suggestion may help avoid technical issues with port allocation in the future.
Step 3
Switch over to the new port by restarting SSH.
#/etc/init.d/ssh restart
Step 4
Verify SSH is listening on the new port by connecting to it. Note how the port number now needs to be declared.
#ssh username@hostname.com -p 50683