As the use of the Internet and other computer networks has grown rapidly in recent years, so has the opportunity for electronic crime. Unlawful activity can be committed or facilitated online. Criminals can trade and share information, mask their identity, identify and gather information on victims, and communicate with co-conspirators. Web sites, electronic mail, chat rooms, and file sharing networks can all yield evidence in an investigation of computer-related crime. This report was developed by the Technical Working Group for the Investigation of High Technology Crimes and is intended to be a resource for individuals responsible for investigations involving the Internet and other computer networks. It is one of a series of electronic crime investigation documents already published or in development by the National Institute of Justice (NIJ). The guides are developed by technical working groups that consist of practitioners and subject matter experts brought together by NIJ to help law enforcement agencies and prosecutors deal with the growing volume and complexity of electronic crime. The series of guides will discuss the investigation process from the first responder, to the laboratory, to the courtroom. Specifically, the guides will address: Electronic crime scene investigation by first responders; Forensic examination of digital evidence; Internet and network investigations; Investigative uses of technology; Courtroom presentation of digital evidence; Development of a digital evidence forensic unit; The recommendations presented in this guide are not mandates or policy directives and may not represent the only correct course of action. The guide is intended to be a resource for those who investigate crimes related to the Internet and other computer networks. It does not discuss all of the issues that may arise in these investigations and does not attempt to cover traditional investigative procedures.