Use a Split-Horizon Architecture

How it is checked

Audit method: Manual review

This recommendation cannot be checked automatically. A scan lists it with these instructions when you pass --include-manual.

Perform the following to audit for compliance: Review the network and DNS architecture, and identify the external authoritative DNS servers along with the internal authoritative DNS servers to ensure they are separate and serve only external and only internal clients respectively. Review the external DNZ zones to ensure only minimal name information is included in the external zones. Perform a query of an internal only name to the external DNS servers to ensure they do not provide a positive response.

How it is fixed

Fix method: Guidance or infrastructure patch

Perform the following for remediation: Implement Split-Horizon Architecture to separate external and internal DNS services. The external DNS servers should respond only to names of approved external services, such as web, email and VPN services.