In recent years, the Internet has provided extremists and terrorists revolutionary new ways to organize, radicalize, and recruit in pursuit of their aims. No longer confined to fringe communities, online extremism is a profound issue across every major social network and has played a role in political conflicts across the globe. In the first half of this course, we will explore the growing corpus of academic research on online extremism. In the second half, we will use open-source tools to collect, process, and analyze data on Internet-based extremists.