Backscatter communication–assisted non-orthogonal multiple access has emerged as a promising candidate for Internet of Things (IoT) networks. At the same time, intelligent reflecting surfaces are widely viewed as a fundamental technology for sixth-generation (6G) systems due to their ability to shape the wireless propagation environment. This paper analyzes the reliability and security performance of a downlink IRS-NOMA architecture that incorporates a backscatter device, under the assumption that all nodes experience hardware impairments (HIs). In the considered setup, one user obtains its signal via the backscatter link, whereas the other user is served through the intelligent reflecting surface, and each transmission is subject to interception by a dedicated eavesdropper. To characterize reliability, we derive closed-form expressions for the outage probability (OP); to quantify security, we examine the intercept probability (IP). Numerical simulations validate the analytical findings and demonstrate that, under practical HIs, the proposed IRS-NOMA framework achieves improved reliability of the system.