This paper studies a wireless powered relaying (WPR) system in which a source transmits an information signal to a destination with the help of an energy constrained relay in the presence of an eavesdropper. This work considers a scenario in the full-duplex WPR system where the information transmission/reception and the energy harvesting are performed simultaneously at the relay. We first derive an achievable secrecy rate of the system and formulate a joint optimization problem of artificial-noise-aided secure beamforming to maximize the achievable secrecy rate. Then, an efficient semi-definite relaxation (SDR) based algorithm is proposed to obtain the optimal beamforming. Furthermore, we also propose three suboptimal beamforming but low computational complexity schemes. Comparisons are carried out among the performances of the proposed optimal and suboptimal schemes.