SSH and SFTP (and SCP)

Trouble with hostkeys?

Telnet, rlogin, and ftp are old programs used to access other computers on the network, but they are now considered very insecure. Hackers can read the information passed between computers when these programs are used. In particular, they can read a user's password when she logs on to a remote computer. Hackers steal such password information to log on to a computer, then to break into its operating system, then launch further attacks on the Internet under a false identity.

Therefore, telnet and rlogin and ftp are not available on C.U. Boulder computers; instead, we use the secure versions named SSH and SFTP (or SCP). These programs use public-key encryption to encrypt all traffic between the computers, so that the hacker listening in will intercept only unbreakably-encrypted gibberish!

Ssh (``secure shell'') is used to log on a remote computer, and sftp (``secure ftp'') or scp (``secure copy'') is used to transfer files between two computers. On Unix computers one types the commands ssh or sftp or scp, respectively. Scp is for Unix systems only, not Macs or PCs. It is a a non-interactive command-line executable which performs a single file transfer. You can use scp commands in scripts and aliases. (See Unix manual pages for ssh and scp and sftp.)

simplified manual page for Unix ssh, scp, sftp

For Macintosh and for Windows/Intel PCs, you can download free and high-quality ssh software from an ITS web page, while for Unix computers, ssh is available as freeware from the Web:

Macintosh OS X: Download security software

Windows 2000/XP: Download security software

Unix: Visit www.openssh.org and download the latest, free, Open Source version of SSH for your own (unix) computer.