An OL 8 firewall must employ a deny-all, allow-by-exception policy for allowing connections to other systems.

An XCCDF Rule

Description

<VulnDiscussion>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. OL 8 incorporates the "firewalld" daemon, which allows for many different configurations. One of these configurations is zones. Zones can be used in 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.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>

ID: SV-248839r958672_rule
Severity: Medium
References: CCI-002314
Updated: 17 days ago

Configure the "firewalld" daemon to employ a deny-all, allow-by-exception policy with the following commands:

     $ sudo firewall-cmd --permanent --new-zone=[custom]

     $ sudo cp /usr/lib/firewalld/zones/drop.xml /etc/firewalld/zones/[custom].xml
This will provide a clean configuration file to work with that employs a deny-all approach.

Note: Add the exceptions that are required for mission functionality and update the short title in the xml file to match the [custom] zone name.

Reload the firewall rules to make the new [custom] zone available to load:
     $ sudo firewall-cmd --reload

Set the default zone to the new [custom] zone:
     $ sudo firewall-cmd --set-default-zone=[custom]

Note: This is a runtime and permanent change.

Add any interfaces to the new [custom] zone:
     $ sudo firewall-cmd --permanent --zone=[custom] --change-interface=ens33

Reload the firewall rules for changes to take effect:
     $ sudo firewall-cmd --reload

An OL 8 firewall must employ a deny-all, allow-by-exception policy for allowing connections to other systems.

Description

Remediation - Manual Procedure