After installation and started the FTP service, anonymous users are given access to your FTP server by default. Supposed you are using WU-FTPD (Washington University FTP Server), it assumes that your firewall is not blocking access to the service and that disable = yes was changed to disable = no in the file /etc/xinetd.d/wu-ftpd. To prevent anonymous users from accessing your FTP server, add the following line to your /etc/ftpaccess file:
[code:1]defaultserver private[/code:1]