V-230504

Discussion

Failure to restrict network connectivity only to authorized systems permits inbound connections from malicious systems. It also permits outbound connections that may facilitate exfiltration of DoD data. RHEL 8 incorporates the "firewalld" daemon, which allows for many different configurations. One of these configurations is zones. Zones can be utilized to a deny-all, allow-by-exception approach. The default "drop" zone will drop all incoming network packets unless it is explicitly allowed by the configuration file or is related to an outgoing network connection.

Check Content

Verify "firewalld" is configured to employ a deny-all, allow-by-exception policy for allowing connections to other systems with the following commands:

     $ sudo  firewall-cmd --state
     running

     $ sudo firewall-cmd --get-active-zones
     [custom]
     interfaces: ens33

     $ sudo firewall-cmd --info-zone=[custom] | grep target
     target: DROP

If no zones are active on the RHEL 8 interfaces or if the target is set to a different option other than "DROP", this is a finding.

If the "firewalld" package is not installed, ask the System Administrator if an alternate firewall (such as iptables) is installed and in use, and how is it configured to employ a deny-all, allow-by-exception policy. 

If the alternate firewall is not configured to employ a deny-all, allow-by-exception policy, this is a finding.

If no firewall is installed, this is a finding.