OpenSSH/PuTTY/SSH is the now ubiquitous program for logging into or executing commands on a remote machine. It provides secure encrypted communications between two untrusted hosts over an insecure network, replacing the hideously insecure telnet/rlogin/rsh alternatives.
- For login to a shell on a remote host (replacing Telnet and rlogin)
- For executing a single command on a remote host (replacing rsh)
- For setting up automatic (passwordless) login to a remote server (for example, using OpenSSH)
- Secure file transfer
- In combination with rsync to back up, copy and mirror files efficiently and securely
- For forwarding or tunneling a port (not to be confused with a VPN, which routes packets between different networks, or bridges two broadcast domains into one).
- For using as a full-fledged encrypted VPN. Note that only OpenSSH server and client supports this feature.