BIND DNS
TMA-BIND-1.4
Use Secure Upstream Caching DNS Servers
Description
Caching name servers often forward queries to another caching name server to allow the name service work to be aggregated and improve performance by taking advantage of the cache of an upstream name server. The default caching name server provided by the Internet service provider is often used in this manner. Manual review: the check needs remote queries, architecture knowledge or site policy.
How it is checked
Audit method: Manual review
Perform the following for an audit: ; Check the network architecture and the identify all internal authorized caching DNS servers configured via DHCP or statically. ; Verify that there are network firewall and access controls rules that prevent internal systems from sending DNS queries directly to unauthorized external DNS servers. Only the authorized internal DNS servers should be allowed to send external DNS queries and they should be configured to only use authorized external DNS servers.
How it is fixed
Fix method: Guidance or infrastructure patch
Perform the following for remediation: ; Select an external DNS provider that sufficiently mitigates malicious DNS traffic to meet your organizational requirements. ; Review network architectural, approved internal DNS servers, and prepare to block outbound DNS traffic, except to the approved DNS servers from the internal caching name servers. ; Review, test and document the approved external DNS servers. ; Configure the internal caching-only DNS servers to forward queries to the approved external caching DNS server. The forwarders directive similar to the example below may be placed in the server options directive. forwarders { acl_of_approved_servers; }
Properties
- Operating systems
- Any
- Tags
- binddnsarchitecture
- Reference
- CIS ISC BIND DNS Server 9.11 Benchmark v1.0.0 - 1.4 Use Secure Upstream Caching DNS Servers