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What is SSH?

SSH is similar to telnet but with encryption.

Secure Shell (SSH) is a program to log into another computer over a network, to execute commands on a remote machine, and to move files from one machine to another. It provides strong authentication and secure communications over unsecure channels. It is intended as a replacement for telnet, rlogin, and rsh. Ssh typically includes scp and sftp, which are secure versions of rcp and ftp.

Why should I use SSH?

SSH protects against:

  • Interception of cleartext passwords and other data by intermediate hosts
  • IP spoofing, where a remote host sends out packets which pretend to come from another, trusted host. Ssh even protects against a spoofer on the local network, who can pretend he is your router to the outside.
  • IP source routing, where a host can pretend that an IP packet comes from another, trusted host.
  • DNS spoofing, where an attacker forges name server records
  • Manipulation of data by persons in control of intermediate hosts

How do I get started using SSH?

Here is a short list of some of the many free SSH programs available:

For Windows:
PuTTY is a free Windows SSH client.

For Macintosh:
Mac OSX comes with a standard UNIX ssh client. Run the Terminal program, then use ssh from the command line.