WAF

Web application firewall (WAF)

A Web application firewall (WAF) is a firewall that monitors, filters or blocks the HTTP traffic to and from a Web application.

A WAF protects a Web application by controlling its input and output and the access to and from the application. Running as an appliance, server plug-in or cloud-based service, a WAF inspects every HTML, HTTPS, SOAP and XML-RPC data packet. Through customizable inspection, it is able to prevent attacks such as XSS, SQL injection, session hijacking and buffer overflows, which network firewalls and intrusion detection systems are often not capable of doing. A WAF is also able to detect and prevent new unknown attacks by watching for unfamiliar patterns in the traffic data. A WAF can be either network-based or host-based and is typically deployed through a proxy and placed in front of one or more Web applications. In real time or near-real time, it monitors traffic before it reaches the Web application, analyzing all requests using a rule base to filter out potentially harmful traffic or traffic patterns. Web application firewalls are a common security control used by enterprises to protect Web applications against zero-day exploits, impersonation and known vulnerabilities and attackers. WAFs started to gain attention when the PCI Security Standards Councilformed and PCI DSS compliance was mandated by the credit card brands for merchants that process payment card transactions. PCI DSS requires that Web applications be fortified through either a code security review or a WAF. Some examples of Web application firewalls include Citrix Systems Inc.'s NetScaler AppFirewall, Fortinet Inc.'s FortiWeb-400C and F5 Networks Inc.'s BIG-IP Application Security Manager.

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