Deep Packet Inspection (DPI) application classification systems and methods are presented to enrich and improve application classification. Specifically, the systems and methods utilize domain and hostname information to enrich the DPI application classification. The systems and methods can include obtaining a packet; determining a hostname associated with the packet; utilizing a main rule to extract a domain from the hostname; and analyzing the domain and the hostname with a plurality of secondary rules based on the domain to deduce an application therefrom.