Title

The firewall must deny network communications traffic by default and allow network communications traffic by exception (i.e., deny all, permit by exception). (Cat I impact)

Discussion

To prevent malicious or accidental leakage of traffic, organizations must implement a deny-by-default security posture at the network perimeter. Such rulesets prevent many malicious exploits or accidental leakage by restricting the traffic to only known sources and only those ports, protocols, or services that are permitted and operationally necessary. As a managed boundary interface, the firewall must block all inbound and outbound network traffic unless a filter is installed to explicitly allow it. The allow filters must comply with the Ports, Protocols, and Services Management (PPSM) Category Assurance List (CAL) and Vulnerability Assessment (VA).

Check Content

Determine the default security policies on the firewall for traffic from one zone to another zone (inter-zone). The default policy must be a "Deny" policy that blocks all inter-zone traffic by default. Ensure no policy that circumvents the default "Deny" inter-zone policy is allowed. Traffic through the firewall is filtered so that only the specific traffic that is approved and registered in the PPSM CAL and VAs for the enclave. Verify rules or access control statements containing "any" for either the host, destination, protocol, or port are not used. If the firewall does not deny all network communications traffic by default and allow network communications traffic by exception (i.e., deny all, permit by exception), this is a finding.

Fix Text

Configure the firewall with a "Deny" inter-zone policy which, by default, blocks traffic between zones and allows network communications traffic by exception (i.e., deny all, permit by exception) in accordance with PPSM CAL and VAs for the enclave.

Additional Identifiers

Rule ID: SV-206694r604133_rule

Vulnerability ID: V-206694

Group Title: SRG-NET-000202

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.