SSH is a standard for remote logins and file transfer over the Internet. It encrypts all traffic, and provides a high level of protection against hacker attacks. Main features of SSH include secure remote logins, terminal emulation, fully integrated secure file transfers, secure tunneling of X11 traffic, and secure access to e-mail over the Internet.

There are many variants of SSH available. Here are a few:

• SecureCRT is a great SSH client that also handles, serial, telnet and ssh1/ssh2 connections.
  

• PuTTY is a free implementation of Telnet and SSH for Win32 platforms.
   

• F-Secure has SSH clients for Windows, MacOS and Unix.
  

• SSH.com has SSH servers and clients for various OS's.
  

• For a Unix implementation of ssh that's free for everyone to use, check out OpenSSH at: http://www.openssh.com