I have been working with Barracuda Web Application Firewall for more than almost three and a half years.
Its main use case is to provide security to applications, to strengthen their security policies, to protect the applications from cyber attacks and to make them compliant against OWASP Top 10. Moreover, it allows only legitimate traffic, reduces false positives, makes application access easy, filters out non-legitimate traffic, verifies what exactly comes within the payload of the request, inspects everything that comes with a request, and fine-tunes according to the application logic based on the contents the application serves to their clients.
For example, if we consider a company that has an application with a payment gateway configured, which provides services including money transactions, we deploy Barracuda Web Application Firewall for that application. We host the service in Barracuda Web Application Firewall. When a client requests access to the application, the request goes to Barracuda Web Application Firewall first, which will verify the request contents and create a separate TCP connection to the backend server if the request is legitimate. This process protects against attacks including SQL injection or cross-site scripting, where Barracuda Web Application Firewall will block any request that matches attack signatures.