When we turn our attention to the fast-growing Internet activities of various radial and terrorist entities, there is an intense need to work on new solutions to develop effective and efficient counterterrorism measures that follow the democratic process, values and freedoms. Knowledge discovery, data mining techniques and data fusion play a central role in improving the counterterrorism capabilities of intelligence, security and law enforcement agencies. The broad diversity of potential sources of web-based and web-focused attacks, our reliance on information systems that are inherently insecure, and the international dimension of both cyber attacks and governmental responses raise a host of complicated policy questions and cultural challenges for governmental security institutions. These include how best to improve the state of cyber security: what can be done to improve international interagency cooperation on stemming cyber crime and preventing and responding to cyber terrorism; and cyber warfare. Having all the challenges in mind, this article will focus on the most important and highly sensitive one, international cooperation. This contribution, written in the style of a discussion paper, highlights the most important factors towards the development and institutionalization of an international interagency collective open source intelligent system regarding the threat of Islamist terrorism.