In this article, we investigate physical layer security in downlink Internet of Things networks under imperfect channel state information (CSI), in which a controller (Alice) intends to serve two user devices (D 1 and D 2) simultaneously by using nonorthogonal multiple access (NOMA). Cooperative jamming (CJ) is introduced as a powerful solution for guaranteeing secure transmission. To be specific, we integrate an unmanned aerial vehicle (UAV) jammer that generates artificial noise to confuse multiple noncolluding eavesdroppers (Eves). Considering only D 1 requires secure transmission, we develop an adaptive power allocation scheme to maximize the secrecy rate at D 1 while meeting the desired quality of service (QoS) threshold at D 2. Furthermore, a strategy can be utilized to obtain the optimal location of the UAV jammer is derived for further performance enhancement. Besides, we also examine the impact of the channel uncertainties on system performance. Numerical results are provided to confirm the superiority and applicability of the proposed CJ scheme over benchmark schemes in terms of secrecy performance and effective energy efficiency.