In this book, we have analyzed the feasibility of outbound traffic i.e. extrusions, to detect and prevent attacks caused because of botnets. As part of the book, a Network-based Detection and Prevention systems of botnets called N-EDPS has been proposed. A number of Botnet profiles along with IP addresses of infected computers, IP addresses of C & C servers of Botnets, and IP addresses of malware download centers have been identified during the live run of the proposed N-EDPS. In the first part of the study, an overview of the botnet problem, botnet defense, the review of defense mechanisms along with their pros and cons is given. The second part of the study focuses on problem formulation and experimental setup of N-EDPS. The third part discusses the various results obtained. And the last part of the thesis concludes the work by highlighting the scope for future work.