The late 20th and early 21st centuries have seen a phenomenal growth in society's use of information technology. Criminals, including terrorists and terrorist organizations, have also adopted information technologies. Information technologies are used to enhance the efficiency, productivity, and effectiveness of terrorist activities and offenses. Investigating terrorist use of information technologies creates a number of challenges for law enforcement officials. While some of the challenges are encountered during conventional criminal investigations, terrorist investigations also present unique challenges. Through content and typological analysis, this study examined open source information to identify, categorize and propose a model of these challenges. Four primary categories were identified: technology, methodology, legal, and administration and human resources challenges.