The use of text mining tool in national defence security domain has become an important issue. Government agencies are investing considerable resources in the surveillance of all kinds of communication, such as email,chats in chat rooms. Email is used in many legitimate activities such as messages and documents exchange. Unfortunately, it can also be misused, for example in the distribution of unsolicited junk mail, mailing offensive or threatening materials. Since time is critical and given the scale of the problem, it is infeasible to monitor emails or chat rooms normally. Thus automatic text mining tools offer a considerable promise in this area. Although not much work has been conducted in this area (compared to bioinformatics), text mining technology is becoming an emergence technology for national security defence. The work of [28] particularly focuses on investigating and determining the gender of the author based on the genderpreferential language used by the author. They claimed thatmen and women use language and converse differently even though they speak the same language. The work has been conducted by using the Support Vector Machine (SVM) developed by T. Joachims from the University of Dortmund. The work of [29] for example, has applied text mining techniques to existing medical literature to identify viruses which can be potentially be used as biological weapon, and where such capability is not yet recognized.
Another example of text mining system is COPLINK system [30]. It was done at University of Arizona in Tucson to help the police to discover the link between agencies.