Tatu Ylonen's SSH encrypted remote login and became the standard

In the early 1990s, telnet, rlogin and FTP carried passwords and data in cleartext, so anyone on the path could read them.

In 1995 Finnish developer Tatu Ylonen built Secure Shell to replace them with one protocol that encrypted the whole session and authenticated the host with keys.

Ylonen gave the implementation away; OpenSSH, a free reimplementation, was bundled into every major Unix and Linux, and the protocol became the way to reach a server.

One encrypted channel replaced telnet and rlogin

It encrypted the entire session including the password, so nothing on the path could be read.

One protocol covered remote shell, file copy and tunneling, so a team replaced several insecure tools at once.

Ylonen gave the code away and OpenSSH made it free on every Unix, so adoption needed no purchase.

Public-key authentication let a client trust a host's identity instead of trusting a shared password every time.

A security standard wins not by being the most advanced but by being the simplest thing that makes the unsafe default unthinkable.

OpenSSH became the bundled default on every major Unix and Linux, and SSH is now the standard way to manage servers and to tunnel traffic; telnet, rlogin and FTP faded to legacy tools.