During a security audit you confirm that external users can run an unrestricted "dig axfr" against the company's Internet-facing DNS server and obtain a full list of host records. To implement an effective footprinting countermeasure while keeping normal name resolution intact, which change should you make on the authoritative server?
Replace A records with CNAME aliases and move DNS service to TCP port 8053.
Enable DNSSEC signing for the public zone to authenticate responses.
Disable recursive queries on the authoritative name server.
Permit zone transfers solely to trusted secondary DNS servers using an IP ACL or TSIG authentication.
An attacker who can perform a full AXFR (zone transfer) against an organization's authoritative DNS server gains an enumerated map of hosts, service names, and sometimes internal addressing. The standard countermeasure is to disable open zone transfers and explicitly allow them only for designated secondary name servers, ideally enforcing the restriction with both an IP-based ACL and/or a TSIG-signed key. This preserves legitimate replication while preventing arbitrary Internet clients from harvesting the zone.
Disabling recursion limits resolver lookups but does not stop AXFR requests. DNSSEC adds integrity and origin authentication but still serves the entire zone. Moving records to CNAMEs or another port does nothing to prevent a standard zone transfer against the authoritative server.
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What is a zone transfer in DNS?
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Reconnaissance Techniques
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