Terrorist organizations increasingly resort to the Internet to promote terrorism, recruit new terrorists, plan and finance their operations. The paper first proposes a definition of terrorism, cyberterrorism, and online terrorism preparatory acts. It then analyses whether current binding international instruments on terrorism, organized crime or cybercrime could prohibit cyber activities precursor of terrorism. The paper concludes that there is no gap in international law that leaves online terrorism related acts completely unregulated. It nevertheless recommends the drafting of an international treaty that would respond more comprehensively, precisely and thus efficiently to the use of the Internet for terrorist purposes.