If you don’t use SSH or SFTP, and instead use telnet or FTP, you’re asking for it. Big time. FTP & telnet send everything - passwords included - in the clear. Not safe at all. But, even if you use SSH (& it’s descendants, SFTP & SCP), there’s always more to learn. SSH offers an incredible amount of cool tricks that enable you to do an amazing amount of stuff. If you want to learn more, check out Brian Hatch’s series of articles on SSH at SecurityFocus. They’re well-written, & Brian definitely knows his stuff. Read ‘em, learn ‘em, live ‘em.