AWS Web Application Firewall: Bolt-on Security for Insecure Websites @ InfoQ
"Web Application Firewall (WAF) is a new feature from AWS which sits in front of your public website and protects it from malicious traffic. It works like a reverse proxy which inspects incoming HTTP requests looking for patterns that indicate suspicious activity. Good requests are passed onto your web application to handle, and bad requests are blocked. It's a tool which can potentially add a layer of security to an existing application without changing the app."