The rapid development of the Internet as a cornerstone of private and social life has provoked a growing effort by law enforcement and security agencies to understand what role the Internet plays in terrorism. Paul Gill, Emily Corner, Maura Conway, Amy Thornton, Mia Bloom, and John Horgan’s (2017, this issue) effort to identify empirically when and how terrorists engage with the Internet is thus timely and important. Understanding when terrorists use the Internet is valuable for investigators who must evaluate the immediacy of the risk posed by a suspect or cell. Knowing the typical patterns of use (or lack of use) can facilitate inferences about a cell’s preparedness, the nature of its support, and even the goal of its attack. Understanding how terrorists use the Internet is essential for policy makers who must construct legislation to deter citizens from terrorism while retaining their rights to freedom. This is arguably best accomplished by legislation targeted at a narrow set of Internet uses that are, as far as possible, exclusively associated with illegal actions.