What would secure a mobile app's network to restrict traffic into the database with customer personal information?

The correct answer effectively highlights the role of network access control lists (ACLs) in securing a mobile app's network when it comes to restricting traffic into a database containing sensitive customer personal information.

Network ACLs function as a layer of security for your Amazon VPC by providing a way to control inbound and outbound traffic at the subnet level. By using ACLs, you can specify which types of traffic are allowed or denied based on factors such as IP address, protocol, and port. This fine-grained control allows for a more secure environment as it enables you to enforce policies that can restrict access to sensitive resources, such as databases that handle personal information.

For example, you could configure an ACL to only allow traffic from known IP addresses that are whitelisted, while blocking all other traffic. This prevents unauthorized access and mitigates the risk of data breaches, making it crucial for maintaining the confidentiality and integrity of customer information.

Thus, network ACLs are instrumental in creating a secure access boundary around the database, making them a suitable choice for the scenario described.