Title

The DNS server implementation must be configured to prohibit or restrict unapproved ports and protocols. (Cat II impact)

Discussion

In order to prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types), organizations must disable or restrict unused or unnecessary physical and logical ports/protocols on information systems. Applications are capable of providing a wide variety of functions and services. Some of the functions and services provided by default may not be necessary to support essential organizational operations. Additionally, it is sometimes convenient to provide multiple services from a single component (e.g., email and web services); however, doing so increases risk over limiting the services provided by any one component. To support the requirements and principles of least functionality, the application must support the organizational requirements by providing only essential capabilities and limiting the use of ports, protocols, and/or services to only those required, authorized, and approved to conduct official business or to address authorized quality of life issues.

Check Content

Review the DNS system configuration to ensure the system is configured for incoming traffic only on UDP/53 and TCP/53 and outgoing DNS traffic sent from a random port rather than the DNS software's default port. If the DNS implementation is not configured for incoming traffic on UDP/53 and TCP/53 and outgoing traffic sent from a random port rather than the DNS software's default port, this is a finding.

Fix Text

Configure the DNS implementation for incoming traffic on UDP/53 and TCP/53 and outgoing traffic sent from a random port rather than the DNS software's default port.

Additional Identifiers

Rule ID: SV-205168r879588_rule

Vulnerability ID: V-205168

Group Title: SRG-APP-000142

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.