A Web Application Firewall (WAF) is a type of cybersecurity technology designed to protect web applications from a variety of attacks, such as SQL injection, cross-site scripting (XSS), and other common web-based threats. A WAF sits between the web application and the internet, monitoring and analyzing incoming traffic in real-time. It can detect and block malicious traffic before it reaches the web application, providing an additional layer of defense against cyber attacks. WAFs can be implemented on-premises or through a cloud-based service and can be configured to suit the specific security needs of the web application they protect. WAF is often required by security standards such as PCI-DSS.