No, you can't, not in any useful way. However, I'm not aware that security is the largest concern here. We're talking about a one time file transfer. I would certainly not suggest ncftp for regular use backing up data because the password does get sent in the clear. Frankly, building the .tar.bz2 file in /tmp might be considered insecure, as anyone might get at it there. The background transfer of ncftp is a very nic feature, though. You can get similar securely with nohup and scp or rsync.
