A company runs an application on a fleet of Amazon EC2 instances that are in private subnets behind an internet-facing Application Load Balancer (ALB).The ALB is the origin for an Amazon CloudFront distribution. An AWS WAF web ACL that contains various AWS managed rules is associated with the CloudFront distribution. The company needs a solution that will prevent internet traffic from directly accessing the ALB. Which solution will meet these requirements with the LEAST operational overhead?