If you want to be unidentifiable, that is entirely up to you, and possible within rules of our server by using password of type:
inconnu@<your host identity> If you want to be totally unknown, you must not use FTP, as it can never be used without revealing your own host identity.There do exist ftp-by-mail servers, and proxy-ftp-servers, which occasionally do reveal their user identity -- send requesting user's address as password. Some gopher and WWW -gateways are able to reveal only users host identity, which in case of a PC or equivalent can be deduced to one particular user.