Definition: AWS web application firewall that protects against common exploits like SQL injection, cross-site scripting, and DDoS attacks.
— Source: NERVICO, Product Development Consultancy
What is AWS WAF
AWS WAF (Web Application Firewall) is Amazon’s web application firewall service that protects applications against common exploits that can affect availability, compromise security, or consume excessive resources. It deploys in front of resources like CloudFront, Application Load Balancer, or API Gateway, inspecting each HTTP request before it reaches the application. AWS WAF allows creating custom rules and using managed rules from AWS or third parties in the AWS Marketplace.
How It Works
WAF operates through Web ACLs (Access Control Lists) containing rules evaluated in priority order. Each rule inspects specific components of the HTTP request: headers, body, query parameters, source IP address, or URL pattern. Possible actions are to allow, block, or count the request. AWS managed rules provide predefined protection against common threats such as SQL injection, cross-site scripting (XSS), malicious bots, and known OWASP Top 10 vulnerabilities. Rate-based rules limit the number of requests from a single IP within a time period, mitigating brute force attacks and application-layer DDoS.
Why It Matters
Web applications exposed to the internet are constant targets of automated attacks. Without a WAF, every vulnerability in the application code is directly exploitable. AWS WAF adds a defense layer that filters malicious traffic before it reaches the application, significantly reducing the attack surface. For applications handling sensitive data or processing payments, a WAF is not optional but a compliance requirement under frameworks like PCI DSS.
Practical Example
A payments platform deploys AWS WAF in front of its Application Load Balancer. AWS managed rules automatically block SQL injection and XSS attempts. A custom rule limits the login endpoint to 100 requests per minute per IP, mitigating brute force attacks. After activation, the WAF blocks 15,000 daily malicious requests that previously reached the application servers, reducing processing load and eliminating false positives from the internal intrusion detection system.