Why a Definition?
Web applications firewalls are not new. The 1st one was introduced in 1997. But web application firewalls did not receive significant market attention until recently.
One of the primary drivers for web application firewalls adaption today is the Payment Card Industry Data Security Standard or PCI for short. PCI offers WAFs as one of two methods to protect web applications, the other being code review. However, until February 2008 PCI fell short of describing what a WAF is and, and discussed later, the clarification provided is hardly sufficient.
