SSH (Secure Shell - bash, csh, tcsh, sh)
SSH is the secure/encrypted version of Telnet offering direct access to your account via the server's shell. The following is taken from the SSH web site at http://www.ssh.com:
Secure Shell (SSH), sometimes known as Secure Socket Shell, is a UNIX-based command interface and protocol for securely getting access to a remote computer. It is widely used by network administrators to control Web and other kinds of servers remotely. SSH is actually a suite of three utilities - slogin, ssh, and scp - that are secure versions of the earlier UNIX utilities, rlogin, rsh, and rcp. SSH commands are encrypted and secure in several ways. Both ends of the client/server connection are authenticated using a digital certificate, and passwords are protected by being encrypted.
Features of the SSH Secure Shell include:
- Protects all passwords and data  
- Full replacement for telnet, rlogin, rsh, rcp, and ftp  
- Fully integrated secure file transfer and file copying  
- Really cool graphical user interface on Windows  
- Automatic authentication of users, no passwords sent in cleartext to prevent the stealing of passwords  
- Multiple strong authentication methods that prevent such security threats as spoofing identity  
- Authentication of both ends of connection, the server and the client are authenticated to prevent identity spoofing, trojan horses, etc.  
- Automatic authentication using agents to enable strong authentication to multiple systems with a single sign-on  
- Transparent and automatic tunneling of X11 sessions  
- Tunneling of arbitrary TCP/IP-based applications, such as e-mail  
- Encryption and compression of data for security and speed  
- Multiple built-in authentication methods, including passwords, public key, SecurID, and host-based authentication  
- Support for PKI (Public Key infrastructure) and hardware tokens (e.g. smart cards) Multiple ciphers for encryption, including e.g. 3DES, Blowfish, Twofish and the AES candidate Rijndael  
- Multiple ciphers for encryption, including e.g. 3DES, Blowfish, Twofish and the AES candidate Rijndael