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Application & OT Security · Intermediate

DNS Zone Transfer (AXFR)

A DNS mechanism for replicating zones between servers that, if allowed to anyone, leaks every record in a domain.

Definition

Zone transfers (AXFR for full, IXFR for incremental) run over TCP port 53 and should be restricted to authorized secondary name servers. A misconfigured server that permits transfers to any requester reveals the full internal map of hosts. Testing for this is a standard recon step.

Example

dig axfr @ns1.example.com example.com

Exam tip

Zone transfers use TCP 53, not UDP; unrestricted AXFR is a classic misconfiguration finding.

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