Hi,
Normally with FTP if you want stuff to be public accessible you use the anonymous login feature. Although the username and password is required the username is always the word "anonymous" and the password can be anything. As a courtesy it is normally the users email address.
For Proftpd there is the <Anonymous> configuration context. If there are no <Anonymous> sections in your proftpd.conf, then no anonymous logins will be allowed - simple.
See
Anonymous for more details.
Thanks,
THP