During a blackbox pen test you attempt to pass IRC traffic over port 80/TCP from...

An application firewall is an enhanced firewall that limits access by applications to the operating system (OS) of a computer. Conventional firewalls merely control the flow of data to and from the central processing unit (CPU), examining each packet and determining whether or not to forward it toward a particular destination. An application firewall offers additional protection by controlling the execution of files or the handling of data by specific applications.

References: http://searchsoftwarequality.techtarget.com/definition/application-firewall