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 queries to retrieve all records for a domain, exposing hosts and their IP addresses. Controlling access to zone transfers (restricting who can perform them) prevents unauthorized disclosure of this sensitive DNS information. Options A, C, and D relate to mail relay security, CGI directory restrictions, and web directory listing respectively—none directly prevent DNS host/IP exposure.
Step-by-step Derivation:
A zone transfer (AXFR query) is a mechanism that replicates entire DNS zone data between servers. If unrestricted, it allows attackers to enumerate all hosts and IPs in a domain. By controlling the source of zone transfers (e.g., allowing only authorized secondary DNS servers), you prevent this reconnaissance attack. Option A (mail relay) is an SMTP security measure. Option C (CGI restrictions) is a web server security measure. Option D (directory listing) is a web server configuration issue. Only option B directly addresses DNS host/IP disclosure prevention.