AWS Web Application Firewall (WAF) protects web applications running on AWS from common web exploits that could compromise security, availability, or consume excessive resources (which in turn could end up costing you a lot of money).
As the name suggests, it is a firewall service for your web applications running on AWS cloud.
You can create custom web security rules to block common attack patterns, and new rules can be deployed within minutes.
You can deploy WAF on CloudFront as part of your CDN configuration or Application Load Balancer in front of your EC2 web servers or origin servers. You can maintain and create the rules using AWS Management Console or API.
You only pay for what you use, and the pricing is based on how many rules are deployed and how many requests your web application receives.
- AWS WAF (AWS KB)