SFTP is like FTP but with encryption.
Here is an excerpt from the FAQ:
SFTP is a program used to transfer files from one computer to another. It provides strong authentication and secure communications over unsecure channels. It is intended as a replacement for ftp.
The system administrators of the FSU Mathematics Department highly recommend that all math faculty, students, and personnel use SFTP instead of ftp, for reasons of security.
SFTP protects against:
|Interception of cleartext passwords and other data by intermediate hosts (i.e. PEOPLE STEALING YOUR PASSWORD)|
|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 people in control of intermediate hosts|
Here is a short list of some of the many free sftp programs available: