A Weblog is a Web site where entries are made in diary style, maintained by its sole author - a blogger, and displayed in a reverse chronological order. Due to the freedom and convenience of publishing in Weblogs, this form of media provides an ideal environment as a propaganda platform for terrorist groups to promote their ideologies and as an operation platform for organizing crimes. In this work, we present a framework to analyze and visualize Weblog social network embedded beneath relevant Weblogs gathered through topic-specific exploration. Link analysis uses the relationships between bloggers to construct the Weblog social network. Content analysis associates similar blog messages to unveil implicit relationships found in the semantics to further improve the Weblog social network analysis. Users can use different interactive information visualization techniques to explore various aspects of the underlying social network at different levels of abstraction. With the capability of analyzing and visualizing Weblog social networks in terrorist and crime related matters, intelligence agencies and law enforcement will be able to have an additional tools and means to ensure the national security.