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4.1.8 Ensure "firewalld" is configured to employ a deny-all, allow-by-exception policy for allowing connections to other systems

Information

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

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.

The operating system 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.

Solution

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

# firewall-cmd --permanent --new-zone=[custom]

# 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. Next, add the exceptions that are required for mission functionality.

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:

# firewall-cmd --reload

Set the default zone to the new [custom] zone:

# firewall-cmd --set-default-zone=[custom]

Note: This is a runtime and permanent change.

See Also

https://workbench.cisecurity.org/benchmarks/19886

Item Details

Category: ACCESS CONTROL, SECURITY ASSESSMENT AND AUTHORIZATION, SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|AC-17(1), 800-53|CA-9, 800-53|SC-7, 800-53|SC-7(5), CAT|II, CSCv7|9.4, Rule-ID|SV-230504r942942_rule, STIG-ID|RHEL-08-040090, Vuln-ID|V-230504

Plugin: Unix

Control ID: d0690d714fd760b98ed0428fe7aca920c75708394a29912617a3c6d29b5cf93c