Web is a platform for users to search for information to fulfill their information needs but it is also an ideal platform to express personal opinions and comments. A virtual community is formed when a number of members participate in this kind of communication. Nowadays, teenagers are spending extensive amount of time to communicate with strangers in these virtual communities. At the same time, criminals and terrorists are also taking advantages of these virtual communities to recruit members and identify victims. Many Web forum users may not be aware that their participation in these virtual communities have violated the laws in their countries, for example, downloading pirated software or multimedia contents. Police officers cannot combat against this kind of criminal activities using the traditional approaches. We must rely on computing technologies to analyze and visualize the activities within these virtual communities to identify the suspects and extract the active groups. In this work, we introduce the social network analysis technique and information visualization technique for the Gray Web Forum - forum that may threaten public safety.