These articles discuss methods for securing the DNS server for authorized users and preventing access to the DNS server.
Domain Name System (DNS) is a distributed database system for managing host names and their associated Internet Protocol (IP) addresses. On IBM® Systems, the DNS server is intended to provide address translation for the internal, secure network (intranet). Using DNS means that people can use simple names, such as "www.ibm.com" to locate a host, rather than using the IP address (xxx.xxx.xxx.xxx).