If you need to connect to Unix or Linux servers, you may be familiar with utilities such as Telnet and FTP. Telnet lets you connect to a command prompt on a machine over the network. The FTP utility transfers files between your machine and a remote server.
If you are using either Telnet or FTP to connect to a sensitive server, but you aren't using a VPN, you're exposing your password to anyone who can access the network you're connected to (perhaps you're on a public network at a wireless hotspot?), the network where the remote server resides, and any network in between.
If the remote server supports it, you can use the SSH protocol to work with a remote machine's command prompt (replacing Telnet) or securely transfer files using scp or sftp (replacing rcp(1) and FTP).
Mac OS X includes an SSH client and server based on OpenSSH (http://www.openssh.org/). The SSH server can be enabled by checking the Remote Login option in System Preferences Sharing.
You can run the SSH client by typing the command ssh user@hostname in the Terminal application, which is located in /Applications/Utilities, as shown here:
Doris-Computer:~ dori$ ssh firstname.lastname@example.org email@example.com's password: ******** Linux gumzilla 2.2.20 #1 Sat Apr 20 11:45:28 EST 2002 i686 unknown Copyright (C) 1993-1999 Software in the Public Interest, and others Most of the programs included with the Debian GNU/Linux system are freely redistributable; the exact distribution terms for each program are described in the individual files in /usr/doc/*/copyright Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent permitted by applicable law. You have mail. Last login: Wed Sep 10 16:05:55 2003 from m018f36d0.tmodns.net dori@gumzilla:~$ cd src dori@gumzilla:~/src$ ls -l total 48 drwxr-xr-x 2 dori dori 4096 Jun 3 03:06 MyDocuments -rwxr-xr-x 1 dori dori 15645 Mar 23 15:57 blosxom_2_0_rc2.cgi -rw-r--r-- 1 dori dori 5572 Apr 25 19:30 blosxom_2_0_rc2.zip -rwxr-xr-x 1 dori dori 960 May 14 09:28 newblog drwxr-xr-x 4 dori dori 4096 Mar 23 23:29 writeback -rw-r--r-- 1 dori dori 9199 Mar 24 16:05 writeback.zip dori@gumzilla:~/src$ logout Connection to as220.org closed.
You can use scp (secure copy) and sftp (secure FTP) as well. To copy a file with scp, use scp filename user@hostname: path, as in scp secret_document.doc firstname.lastname@example.org:MyDocuments/.
To use sftp, specify the user@hostname, and log in with your password. You can then use ftp commands such as put (to upload a file to the server) and get (to download a file from the server):
Doris-Computer:~ dori$ sftp email@example.com Connecting to as220.org... firstname.lastname@example.org's password: ******** sftp> cd MyDocuments sftp> put secret_document.doc secret_document.doc 100% 0 0.0KB/s --:-- ETA sftp> get super_secret.doc super_secret.doc 100% 8 0.0KB/s 00:02 sftp> quit Doris-Computer:~ dori$
For more information, consult the ssh manpage (run the command man ssh in Terminal).