In this study, the authors give an overview about current trends in botnet development and defense. They start off by giving an overview of botnet technology and introducing core concepts. This is followed by a description of measures employed by botnet operators to secure their botnets against infiltration by security researchers and authorities. The authors discuss both the technical requirements of setting up and operating a botnet as well as the requirements with regard to skills, resources and time of infiltrating and taking down a botnet. The article is concluded with an outlook on future developments.