Block HTTP requests based in X-Forwarded for

Hello,

a. Is it possible with FWB to block certain HTTP requests, carrying illegal IP addresses in the X-Forwarded-for header? (for example 423.121.1.1)

b. An FWB is in front of a web server and this web server communicates to an application server, like this:

FWB------web server----application server

The web server opens a new session to the application server using HTTP at a custom port. In that case, can the FWB protect the application server too?

Thanks

Andreas