A system for identifying perpetrators of fraudulent activity includes location logic for locating, extracting, or capturing identifying information from a client communication received from a client device. For example, the location logic may locate, or extract, a variety of message headers from an HTTP client request. The system may also include analyzer logic to analyze the identifying information, for example, by comparing the identifying information with previously captured identifying information from a previously received client communication. Finally, the system may include account identifier logic to identify user accounts associated with the previous client communication in which the same identifying information was extracted.