In this short position paper, we present a few concrete experiences of Visual Analytics (VA) over big data; as our experiences have been gained on the application domains of cyber-security and Open Source Intelligence (OSINT), which are very relevant and crucial domains targets of possible Virtual Research Environments (VREs), we also discuss and propose an high-level reference architecture and pipeline for a Big Data service in VREs dealing with such aspects, in which the VA part is crucial in order to provide effectiveness to users.