When an FTP server has no access restriction, the FTP server allows any and every user to access its files, we call these servers Anonymous Ftp servers.
Although the Anonymous Ftp server has unrestricted access, it usually still has a logon procedure. Most Anonymous Ftp servers are set up to accept "anonymous" as the user identification. For the password, they accept without paasword and sometimes requires the user's e-mail address. Entering your e-mail address is a courtesy to the site's owners and gives them an idea of who is accessing their files.
We restrict Anonymous Ftp services. It means we require a user identification code and password before allowing access to our files.