How AWS WAF Protects Your Application Load Balancer: WebACL Setup with Managed Rule Groups
When SQL injection and cross-site scripting attacks reach your Application Load Balancer, they hit your application tier directly — WAF is the layer that intercepts and blocks them before a single malicious byte reaches your backend. This post walks through attaching an AWS WAF WebACL to an ALB using AWS Managed Rule Groups, covering the architecture, CLI setup, and the operational details that documentation glosses over. TL;DR: AWS WAF on ALB — Key Facts Aspect Detail WAF scope for ALB REGIONAL (not CLOUDFRONT) Attachment model WebACL associated to ALB ARN SQL injection protection AWSManagedRulesSQLiRuleSet XSS protection AWSManagedRulesCommonRuleSet (contains XSS rules) Default action ALLOW (explicit BLOCK rules override) Rule evaluation order Priority integer — lower number evaluated first Logging destination CloudWatch Logs, S3, or Kinesis Data Firehose How AWS WAF Works with an A...