I know you can telnet to SMTP, POP, IMAP, and FTP, send mail, download mail and download files with these services. I know this is a security concern and there are several ways to protect this from happening. I've also been told you can telnet to port 80 and do various things there. What I'm wondering what damage can an attacker do if they wear to gain unathorized access to this port, how would they do it and what you can do to prevent this. I've tried telnetting to a friends server(with his permission of course) on port and see if I could figure it out myself. Any input or further references to this subject would be greatly appreciated.