mail.sample.org has address 256.0.0.3 webmail.sample.org has address 256.0.0.4 ftp.sample.org has address 256.0.0.5 foo.sample.org has address 256.0.0.6 In most cases, the DNS Zone Transfer policies will be set by your domain name provider; and most providers automatically limit anonymous zone transfers. If yours does not, you will need to work with their support team to prevent this, or switch to a different DNS provider. If your organization maintains its own DNS servers, the administrator of those servers should check the zone transfer policies to prevent anonymous transfers. Page 43 of 240