Telnet and ftp send passwords over the network in clear text that can be easily sniffed. You should replace them with more modern tools such as ssh and scp. SSLtelnet/SSLftp are also available but do not seem to be in such wide use.
SSH is a better telnet than telnet -- it even handles remote X sessions transparently, letting you ssh into another machine and run X aps there with the display automagically exported to your local X server. Give it a try: log on to your ISP from an X term using ssh and type something like xeyes &.