Nowadays, last generation of smartphones are comparable to desktop computers in terms of computational capabilities. Such characteristics can turn a smartphone into a mobile attack vector. In this paper we analyze the use of mobile devices to perpetrate cyber attacks. We present a mobile threat, SlowDroid, running on Android operating system. Such menace implements a Denial of Service attack and it is particularly suitable to a mobile execution, since it makes use of low amounts of computational and bandwidth resources. We present in detail SlowDroid implementation and our choices in terms of design, graphical user interface, and system architecture.