Traditional approaches to understanding the spread of terrorism and infectious diseases are based on 20th century communication models, such as newsletters, face-to-face meetings, and clinic reports. With the new media (e.g., the Web and online social networks), scientists can trace geographic and chronological patterns to reveal the nature of significant events such as radical concepts or epidemic outbreaks. This symposium will focus on the advancement of Web surveillance methodologies developed in the fields of information management, GIScience, linguistic ontology, complex networks, and epidemiology. Innovative Web search tools, intelligence ranking algorithms, space-time analysis, user-generated contents, and social networks will be highlighted in the symposium to demonstrate this new research direction. The Web, a powerful platform for collective thinking and idea exchange, provides valuable intelligence to help scientists monitoring processes ranging in diversity from the spread of diseases to the structure of terrorist networks. The information dynamics can be transformed into visual maps and information landscapes for space-time analysis. Understanding the diffusion and cluster patterns in response to terrorist movements and epidemics may significantly facilitate intervention, and eventually, prevention responses.