The destruction made by nuclear, biological and chemical weapons used by governments and terrorist groups in the near history is posing anxiety and fear for human being. Rumour about the possible use of these agents leads to the development of serious negative effects on populations. Since there are no vaccine and therapy for most viral agents and cost of production as biological weapons is low, interest rate is rising for viruses. In this review, general characteristics, diagnosis, therapy and protective measures for viral agents such as variola virus, hemorrhagic fever viruses, encephalitis viruses, Hantaviruses and Nipah viruses, those can be used as biological weapon, have been summarized.