Ensure Unnecessary Services and Ports Are Not Accepted

Description

Services and ports can be accepted or explicitly rejected or dropped by a zone. For every zone, a default behavior can be set that handles incoming traffic that is not further specified. Such behavior is defined by setting the target of the zone. The possible options are: - ACCEPT - accepts all incoming packets except those disabled by a specific rule. - REJECT - disables all incoming packets except those that have been allowed in specific rules and the source machine is informed about the rejection. - DROP - disables all incoming packets except those that have been allowed in specific rules and no information sent to the source machine.

Rationale

To reduce the attack surface of a system, all services and ports should be blocked unless required.