Simple definition
One WAF protects a web application by filtering requests HTTP.
Technical definition
Web Application Firewall analyzes the application layer and can apply rules against attacks such as injection or crossing the path.
What is it used for?
reduce exposure to public web applications.
Practical example
one WAF blocks a query containing a manifestly malicious SQL load.
Common issues
- too strict a rule
- application not compatible
- poorly inspected traffic bypass
Key takeaway: Always adapt the diagnosis to the product version and the architecture actually deployed.