15 - Restrict Recursive Queries

Information

A recursive DNS query is your typical DNS query from a client. It places the burden of finding the answer on the DNS server which will recursively query other DNS servers authoritative for the domains, until it gets the answer which is then returned to the client. Typically, the DNS server will then cache the answer to that query until its time-to-live expires in order to provide a quick answer to future queries for the same name. BIND can be configured to restrict fulfillment of recursive lookups to only authorized network segments and hosts. This is made possible by the allow-recusion option. It is recommended that this option be utilized to restrict access to the server's recursive lookup capabilities.

Rationale:

If the allow-recursion is not properly configured, malicious entities may abuse this capability for asymmetric load based denial of service attacks, associate the DNS server with SPAM campaigns, or increase the probability of poisoning the server's cache.

Solution

Insert the following either into the global options or to every zone section
allow-recursion { localhost; trusted_clients };

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-20

Plugin: Unix

Control ID: 287c907a95b09b7023e2b70623cc2f2aa07c5ad5c8822490b3af19918c64c55c