<p>The network performance in intelligent reflecting surface (IRS) assisted non-orthogonal multiple access (NOMA) networks is investigated when an eavesdropping scenario is also considered. In fact, IRS method is proposed due to deep shadowing or obstacles between the transmitter and receiver. IRS is distributed to improve the quality of the user’s communications with the base station. Specifically, the secrecy outage probability (SOP) is driven over Nakagami-m fading channels. We also investigate the impact of different network parameters such as the phase shift of IRS reflecting elements, the transmission time and power allocation coefficients to the users on the overall network performance. Therefore, the problem of maximizing the users’ secrecy rate is formulated by the network parameters optimization while the constraint on SOP and transmission time are satisfied. An iterative algorithm is considered based on the particle swarm optimization (PSO) algorithm to solve the problem and enhance the network performance. Monte- Carlo simulations validate the analytical results of the proposed method in increasing secrecy rate of the users and secrecy outage probability enhancement.</p>