The Internet is a powerful political instrument, which is increasingly employed by terrorists to forward their goals. The five most prominent contemporary terrorist uses of the Net are information provision, financing, networking, recruitment, and information gathering. This article describes and explains each of these uses and follows up with examples. The final section of the paper describes the responses of government, law enforcement, intelligence agencies, and others to the terrorism-Internet nexus. There is a particular emphasis within the text on the UK experience, although examples from other jurisdictions are also employed.