proftpd question

Hi,

I am running proftpd on my debain install. From my log, I see once awhile, people are trying to login to my ftp server from variuos ip address.

I am running the ftp just for personal use, disallowed anonymous login already and have the login error out as quick as possible.

I am new to linux, and I would like to know what is the best way to prevent people to try logging into or "test" my ftp server? Or put in the other way, what is the correct way to prevent such act or to protect the ftp server.

Thanks,

Kevin