A scalable method, system, and apparatus for non-intrusively auditing and improving security assessments includes capturing, storing, presenting, displaying, inspecting, monitoring, and analyzing data flow in client-server security assessments and/or network/infrastructure security assessments. The invention provides interested parties with a mechanism to non-intrusively audit in real-time the vulnerability test effort, as well as review, replay, and analyze all aspects of the security assessment during and after the test. For web application assessments, the data capture includes one of the following or some combination: an intermediary with all data passing through the intermediary; a sniffer that can passively extract all data being communicated between the application and tester; and a plurality of computing modules (e.g., software, appliances, etc.) installed in the tester environment or within the application system environment (e.g., software installed on the tester's computer, or on the computer where the intermediary is running, or software installed on the application systems proxy or web server, or an appliance in either environment) for storing, processing, analyzing, reporting, and displaying the data.