A security gateway appliance is configured to evaluate network traffic according to security rules that classify traffic flows according to specifically identified application programs responsible for producing and/or consuming the network traffic and to enforce policies in accordance with network traffic classifications. The appliance includes an on-box anti-virus/anti-malware engine, on-box data loss prevention engine and on-box authentication engine. One or more of these engines is informed by an on-box dynamic real tie rating system that allows for determined levels of scrutiny to be paid to the network traffic. Security gateways of this type can be clustered together to provide a set of resources for one or more networks, and in some instances as the backbone of a cloud-based service.