What is application firewalls?

Application firewalls are security devices, often implemented as a proxy, that examine the application layer (Layer 7) traffic of network communications. They are designed to identify and block malicious requests and attacks targeting specific applications, such as web applications. Common uses include preventing SQL injection, cross-site scripting (XSS), and other application-layer exploits. Unlike traditional network firewalls that operate at lower layers (like network and transport layers) and focus on IP addresses and ports, application firewalls understand the specific protocols (e.g., HTTP, SMTP, DNS) used by the application and can therefore enforce more granular security policies.