OL 9 must be configured to prohibit or restrict the use of functions, ports, protocols, and/or services, as defined in the Ports, Protocols, and Services Management (PPSM) Category Assignments List (CAL) and vulnerability assessments.

To prevent unauthorized connection of devices, unauthorized transfer of information, or unauthorized tunneling (i.e., embedding of data types within data types), organizations must disable or restrict unused or unnecessary ports, protocols, and services on information systems.

Verify OL 9 is configured to prohibit or restrict the use of functions, ports, protocols, and/or services that are unnecessary or prohibited.

Inspect the firewall configuration and running services to verify which services are currently active with the following command:

$ sudo firewall-cmd --list-all-zones custom (active) target: DROP icmp-block-inversion: no interfaces: ens33 sources: services: dhcpv6-client dns http https ldaps rpc-bind ssh ports: masquerade: no forward-ports: icmp-blocks: rich rules:

Ask the system administrator for the site or program PPSM Component Local Service Assessment (CLSA). Verify the services allowed by the firewall match the PPSM CLSA.

If there are additional ports, protocols, or services that are not in the PPSM CLSA, or there are ports, protocols, or services that are prohibited by the PPSM CAL, this is a finding.

Update the firewall settings and/or running services to comply with the PPSM CLSA for the site or program and the PPSM CAL.

Then run the following command to load the newly created rule(s):

$ sudo firewall-cmd --reload