AWS Network Firewall now uses "Application drop established (server-directed only)" as the default stateful action for all newly created firewall policies, replacing the previous default of "Application drop established (bidirectional)" (formerly named "Application layer drop established"). No action is required to benefit from this change when creating new policies. AWS Network Firewall is a managed service that lets you deploy network protections across your Amazon VPCs. Previously, the “Application drop established (bidirectional)” default could silently drop legitimate server-to-client TCP
Source: AWS What's New — read the full report at the original publisher.