Imperva Cloud Application Security - Deploy your applications and data where you want. When you want. Imperva keeps them secure in the cloud, on premises, and in hybrid clouds.
Barracuda Web Application Firewall - Barracuda Web Application Firewall offers security and DDoS protection against automated & targeted attacks.
Sucuri - Website Protection, Malware Removal, and Blacklist Prevention
AWS WAF - AWS WAF is a web application firewall that helps protect your web applications from common web exploits.
Incapsula - Incapsula is a Security CDN that makes any website safer, faster and more reliable. 5 minute setup will make a world of difference.
ModSecurity - ModSecurity is an Open Source web application firewall developed by Trustwave's SpiderLabs.