V-272400

Discussion

Poorly constructed NS records pose a security risk because they create conditions under which an adversary might be able to provide the missing authoritative name services that are improperly specified in the zone file. The adversary could issue bogus responses to queries that clients would accept because they learned of the adversary's name server from a valid authoritative name server, one that need not be compromised for this attack to be successful. The list of secondary servers must remain current with any changes to the zone architecture that would affect the list of secondaries. If a secondary server has been retired or is not operational but remains on the list, an adversary might have a greater opportunity to impersonate that secondary without detection, rather than if the secondary were actually online. For example, the adversary may be able to spoof the retired secondary's IP address without an IP address conflict, which would not be likely to occur if the true secondary were active.

Check Content

Verify that each name server listed on the BIND 9.x server is authoritative for the domain it supports.

Inspect the "named.conf" file and identify all of the zone files that the BIND 9.x server is using.

zone "example.com" {
file "zone_file";
};

Inspect each zone file and identify each NS record listed.

86400 NS ns1.example.com
86400 NS ns2.example.com

With the assistance of the DNS administrator, verify that each name server listed is authoritative for that domain.

If name servers are listed in the zone file that are not authoritative for the specified domain, this is a finding.