Information
Services and ports can be accepted, explicitly rejected, or dropped by a zone.
For every zone, you can set a default behavior that handles incoming traffic that is not further specified. Such behavior is defined by setting the target of the zone. There are three options - ACCEPT REJECT and DROP
- ACCEPT - you accept all incoming packets except those disabled by a specific rule.
- REJECT - you disable all incoming packets except those that you have allowed in specific rules and the source machine is informed about the rejection.
- DROP - you disable all incoming packets except those that you have allowed in specific rules and no information sent to the source machine.
Note: The target may also be set to a fourth option, default The default target provides a convenient way to implement a "deny by default, allow by exception" policy within a firewalld zone, while still allowing essential ICMP traffic.
To reduce the attack surface of a system, all services and ports should be blocked unless required
NOTE: Nessus has provided the target output to assist in reviewing the benchmark to ensure target compliance.
Solution
Run the following command to remove an unnecessary service:
# firewall-cmd --remove-service=<service>
Example :
# firewall-cmd --remove-service=cockpit
Run the following command to remove an unnecessary port:
# firewall-cmd --remove-port=<port-number>/<port-type>
Example :
# firewall-cmd --remove-port=25/tcp
Run the following command to make new settings persistent:
# firewall-cmd --runtime-to-permanent