1. A computer system for identifying and extracting content from data traffic, the system comprising: a capture driver arranged to monitor data traffic and to copy data packets from the traffic to a buffer without disrupting the traffic flow, and to generate pointer information to identify specific parts of a data packet; a plurality of decoder modules, each module being adapted to decode one or more specific data transfer protocols; and a control interface adapted to receive pointer information from the capture driver, to route the pointer information to one or more of the plurality of decoder modules, and to route extracted content from the data traffic to an application, wherein the control interface is adapted systematically to send pointer information relating to the captured data packet to decoder modules in turn until either a module accepts the data or until there are no more modules to try.