This NIJ Special Report documents results of testing dd GNU fileutils 4.0.36, provided with Red Hat Linux 7.1, against the Computer Forensics Tool Testing (CFTT) project's Disk Imaging Tool Specification. The test results provide information for toolmakers to improve tools used in computer forensics investigations, users to make informed choices, and the legal community and others to understand the tools' capabilities. The CFTT project, which is supported by NIJ, the National Institute of Standards and Technology, the U.S. Department of Defense, the Technical Support Working Group, and other related agencies, provides measurable assurance to practitioners, researchers, and other applicable users that the tools used in computer forensics investigations provide accurate results.