WAFs

WAFs provide additional security between users and web applications to protect web servers from unauthorized access and malicious attacks. WAF vendors offer hardware, software, virtual, and cloud-based firewall solutions. Web applications are extremely vulnerable and are also the backbone of business, so they must be protected. The biggest challenge in application security is detecting a vulnerability in your application, at which point the trouble begins when you are patching and fixing the code, as these are time-consuming tasks. This is where WAFs come in; as soon as a vulnerability is detected, you can apply patches to WAF. Any request which comes after the WAF patches are updated will stop attacks associated with the vulnerability that has been found. 

Let's take a look at the following diagram. Non-HTTP/HTTPS attacks are blocked by a perimeter...