Gary McGraw, the CTO of software security firm Cigital, just published an article on Dark Reading called "Beyond the PCI Bandaid". Some tidbits from his article:
Web application firewalls do their job by watching port 80 traffic as it interacts at the application layer using deep packet inspection. Security vendors hyperbolically claim that application firewalls completely solve the software security problem by blocking application-level attacks caused by bad software, but that’s just silly. Sure, application firewalls can stop easy-to-spot attacks like SQL injection or cross-site scripting as they whiz by on port 80, but they do so using simplistic matching algorithms that look for known attack patterns and anomalous input. They do nothing to fix the bad software that causes the vulnerability in the first place.Gary's got an excellent reputation fighting information security problems from the software development perspective. His Silver Bullet podcast series is one of a kind, interviewing everyone from Peter Neumann (one of the founding fathers of computer security) to Bruce Schneier (the most well known of the gurus) to Ed Felten (of Freedom to Tinker and Princeton University fame). He is also the author of several very well respected software security books.