The present invention provides a methodology to thwart attacks that utilize consecutive hypertext transport protocol packets with similar structures, arriving from a plurality of computer systems on a network, such as the Internet, destined for a single or more computer systems on a secondary network, at such a rate with sufficient complexity to produce an effect on the target computer system or systems such that legitimate clients are denied access to requested services, thus creating a “denial of service” situation. The methodology focuses on the dynamic and proactive reassessment of data packet payload content to maintain a running value of similarity or dissimilarity, thus permitting intermediary apparatuses that are performing this computation to create distinction between legitimate clients and illegitimate clients.