In this paper, we analyze the secrecy performance of a cooperative communication wireless system using nonorthogonal multiple access (NOMA) over α − µ fading channel. A new cooperative NOMA scheme is proposed to protect the confidential communication that is transmitted from a source to two users by the help of a relay under the monitoring of an eavesdropper (EAV). In particular, the legitimate user generates jamming signals to the EAV while the source transmits the signals to the relay and the source sends jamming signals to the EAV while the relay forwards the signals to the users. In order to evaluate the secrecy performance, the physical layer security (PLS) in term of the secrecy outage probability (SOP) for the active protection scheme (APS) is investigated and compared to that for a benchmark non-protection scheme (NPS). Simulation results show that the APS can effectively enhance the secrecy performance.