Which AWS service or feature can a user configure to limit network access at the subnet level?

Explanations:

AWS Shield is a managed DDoS protection service that safeguards applications running on AWS. It does not provide capabilities for limiting network access at the subnet level.

AWS WAF (Web Application Firewall) is a service that protects web applications from common web exploits. It operates at the application layer and does not manage network access at the subnet level.

Network ACLs (Access Control Lists) are used to control inbound and outbound traffic at the subnet level in a VPC. They provide a way to set rules that limit access based on IP protocol, port number, and source/destination IP address.

Security groups act as virtual firewalls for EC2 instances to control inbound and outbound traffic. However, they are associated with instances and operate at the instance level, not at the subnet level.