V-269246

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. AlmaLinux OS 9 incorporates the "firewalld" daemon, which allows for many different configurations. One of these configurations is zones. Zones can be used 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 the AlmaLinux OS 9 "firewalld" is configured to employ a deny-all, allow-by-exception policy for allowing connections to other systems.

First ensure firewalld is running:

$  firewall-cmd --state

running

Next, get the active zones:

$ firewall-cmd --get-active-zones

public
  interfaces: enp1s0

Check the target of the zones returned from the previous command:

$ firewall-cmd --info-zone=public | grep target

   target: DROP

Check the runtime and permanent rules match:

$ firewall-cmd --permanent --info-zone=public | grep target

   target: DROP

If no zones are active on the AlmaLinux OS 9 interfaces or if runtime and permanent targets are set to a different option other than "DROP", this is a finding.