I don't use the the web interface to upload files to the FriHost server. I know they will be secure. I use FTP (FileZilla).
How secure is this method..?
Yeah SFTP is great, if you don't have access to that a good thing to do is put your files in a RAR archive, set a secure password and tick "encrypt file names". AES is a good encryption, think winrar is 128 or 256
The transmission itself is not secure, especially in text mode. anybody with the right skill can easily see the whole text file. Binary mode is a bit different. You need almost the whole file to "make sense" of the information, and as each packets might be send to different port, people/bot might "think" it's a packet from different app. Beside, too much packet to capture and put back in sequence for normal ftp operation. Not really worth it.
The real question is, how secure is frihost server. You need to worry about that because it's much easier to get into a server than to capture packet in transmission.
thx everyone.... Great selection of answers..