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AlmaLinux OS 9 firewall must employ a deny-all, allow-by-exception policy for allowing connections to other systems.

Overview

Finding IDVersionRule IDIA ControlsSeverity
V-269246ALMA-09-018830SV-269246r1050780_ruleCCI-000366medium
Description
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.
STIGDate
Cloud Linux AlmaLinux OS 9 Security Technical Implementation Guide2026-02-27

Related Frameworks

1 mapping across 5 frameworks
SCF0 mappings

No source states a mapping between these directly.

Also reachable in 3 hops (8) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

CFG-01Configuration Management Program
1.00
END-01Endpoint Device Management (EDM)
1.00
END-04Malicious Code Protection (Anti-Malware)
1.00
END-06Endpoint File Integrity Monitoring (FIM)
1.00
MON-01Continuous Monitoring
1.00
MON-01.7File Integrity Monitoring (FIM)
1.00
CFG-02Secure Baseline Configurations
0.50
CFG-02.7Approved Configuration Deviations
0.50
NIST 800-530 mappings

No source states a mapping between these directly.

Also reachable in 2 hops (100) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

AC-12Session Termination
1.00
AC-16(1)Dynamic Attribute Association
1.00
AC-17(1)Monitoring and Control
1.00
AC-2Account Management
1.00
AC-2(1)Automated System Account Management
1.00
AC-2(11)Usage Conditions
1.00
AC-2(3)Disable Accounts
1.00
AC-2(4)Automated Audit Actions
1.00
AC-24(1)Transmit Access Authorization Information
1.00
AC-25Reference Monitor
1.00

+90 more (top 10 by confidence shown)

NIST 800-1710 mappings

No source states a mapping between these directly.

Also reachable in 3 hops (2) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

3.4.1
1.00
3.4.2
1.00
CCI1 mapping
CCI-000366
1.00
NIST CSF 2.00 mappings

No source states a mapping between these directly.

Also reachable in 3 hops (5) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

DE.CM-09
1.00
PR.PS-01
1.00
PR.DS-10
0.50
PR.PSPlatform Security
0.50
PR.PS-05
0.50

Who does this work

10 NICE work roles and 9 EC-Council certifications.

This is an inference across published mappings, not a single claim by anyone. This check maps to a control, which maps to a Cybersecurity Framework outcome, which NIST assigns to the work roles below. EC-Council separately maps its certifications to those same roles.

A certification prepares someone for a role. It is not evidence that a holder is qualified, and neither NIST nor EC-Council has stated that any certification here addresses this check.

Work-role assignments published by NIST (NICE Framework Components 2.2.0 and the CSF 2.0 OLIR crosswalk). Certification mappings published by EC-Council.

Details

Check Text (C-269246r1050780_chk)

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.

Fix Text (F-73178r1050780_fix)

Configure the "firewalld" daemon to employ a deny-all, allow-by-exception. Start by adding the exceptions that are required for mission functionality to the "drop" zone. If SSH access on port 22 is needed for example, run the following command: $ firewall-cmd --permanent --add-service=ssh --zone=drop Set the default zone to the "drop" zone: $ firewall-cmd --set-default-zone=drop Note: This is a runtime and a permanent change. Add any interfaces to the newly modified "drop" zone: $ firewall-cmd --permanent --zone=drop --change-interface=enp1s0 Reload the firewall rules for changes to take effect: $ firewall-cmd --reload Check zones and interfaces: $ firewall-cmd --get-active-zones drop interfaces: enp1s0 Check new default zone's target is set to "DROP": $ firewall-cmd --permanent --info-zone=drop | grep target target: DROP The same outcome is achieved by creating a new zone, for example: $ firewall-cmd --permanent --new-zone=stig $ firewall-cmd --reload $ firewall-cmd --permanent --change-interface=enp1s0 --zone=stig $ firewall-cmd --permanent --add-service=ssh --zone=stig $ firewall-cmd --permanent --set-target=DROP --zone=stig $ firewall-cmd --set-default-zone=stig