This paper describes a testbed for experimentally evaluating stepping stone attack attribution techniques. There is a lack of comprehensive experimental evaluation of many different stepping stone attack detection schemes. Therefore, there are no objective, comparable evaluation results on the effectiveness and limitations of these schemes. In this research, we designed and built a scalable testbed environment that can evaluate all existing stepping stone attack attribution schemes reproducibly, provide a stable platform for further research on this area and be easily reconfigured, expanded, and operated with user-friendly interface. This testbed environment has been established in a dedicated stepping stone attack attribution research laboratory. An evaluation of proposed stepping stone techniques is currently underway.