Q1 Choose the DNS server setting that will prevent an existing host and its IP address from...
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Choose the DNS server setting that will prevent an existing host and its IP address from being known.
Show answer & explanation
Zone transfers allow DNS servers to replicate zone data, which contains mappings of hostnames to IP addresses. By controlling access to zone transfers (restricting who can request them), you prevent unauthorized parties from discovering all hosts and their IPs within a domain. Options A, C, and D relate to mail relay, CGI execution, and web directory listing respectively—none of which directly prevent DNS host/IP disclosure.
Step-by-step Derivation:
DNS zone transfers (AXFR queries) expose the complete DNS zone file, revealing all hostnames and their associated IP addresses. Restricting zone transfer access to only authorized secondary DNS servers is a fundamental DNS security practice. Option B directly addresses this vulnerability. Options A (mail relay), C (CGI restrictions), and D (directory listing) are unrelated to DNS host discovery or belong to different security domains (SMTP, web server, HTTP).