Next: Port Monitoring/Scanning
FTP and telnet are well known for their insecure nature. The passwords sent to these two servers can be easily sniffed and they fall easily to buffer overflow attacks. The reason that they are in such high use is that they are old legacy applications. Almost all of the old networking servers have both ftp and telnet. Many of the online web services allow you to publish pages or copy them to the server via ftp. The best thing to know is that if you are using ftp or telnet, you are likely to have problems. Now you have been warned.
FTP and telnet