The first communication protocols that were used on the internet tended to be unencrypted. These protocols such as HTTP, SMTP, FTP and Telnet were much simpler to deploy and required much less expensive hardware to run.
The modern internet is a very different place from where it started. Encrypted communications are becoming the norm for all internet traffic and should be employed in all available situations.
If you have a linux server then administering it will require logging into a terminal. The old, insecure way of accessing the server was by using Telnet. In the mid-1990's this was replaced with SSH which has not become a versatile, encrypted protocol capable of encrypting the login to a remote terminal and also encrypting file transfers.
The following documentation covers the use of SSH to log into a remote linux server from a local Windows or linux computer:
The final page explores using SSH to securely transfer files to a linux server from a Widows and Linux computer:
Last updated 22 June 2017, 06:53 GMT