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In a split DNS configuration, where separate name servers are used between the external and internal networks, the internal name server must be configured to not be reachable from outside resolvers.


Finding ID Version Rule ID IA Controls Severity
V-259416 WDNS-22-000119 SV-259416r945368_rule Medium
Instead of having the same set of authoritative name servers serve different types of clients, an enterprise could have two different sets of authoritative name servers. One set, called external name servers, can be located within a DMZ; these would be the only name servers that are accessible to external clients and would serve resource records (RRs) pertaining to hosts with public services (web servers that serve external web pages or provide business-to-consumer services, mail servers, etc.). The other set, called internal name servers, is to be located within the firewall and should be configured so the servers are not reachable from outside and hence provide naming services exclusively to internal clients.
Microsoft Windows Server Domain Name System (DNS) Security Technical Implementation Guide 2024-01-09


Check Text ( C-63155r939951_chk )
Consult with the system administrator to review the internal Windows DNS Server's firewall policy.

The inbound TCP and UDP ports 53 rule should be configured to only allow hosts from the internal network to query the internal DNS server.

If the firewall policy is not configured with the restriction, consult with the network firewall administrator to confirm the restriction on the network firewall.

If neither the DNS server's firewall policy nor the network firewall is configured to block external hosts from querying the internal DNS server, this is a finding.
Fix Text (F-63063r939952_fix)
Configure the internal DNS server's firewall policy, or the network firewall, to block queries from external hosts.