In this paper, we first investigate secure communications for a two-hop interference relay system in the wireless Internet of Things (IoT), where K source-destination pairs communicate in the presence of an eavesdropper. Explicitly, we jointly design source, relay and destination matrices upon minimizing total mean-squared error (MSE) of all legitimate destinations while keeping the MSE at eavesdropper above a certain threshold. We illuminate that the joint design of the source, relay and destination matrices subject to both secrecy and transmit power constraints. More specifically, we proposed an efficient iterative distributed algorithm to simplify the process of the joint design for optimal source, relay and destination matrices. Furthermore, the convergence of the iterative distributed algorithm is described. Additionally, the performances of the proposed algorithm, including both its secrecy rate and MSE, are characterized with the aid of simulation results. We demonstrate that our proposed algorithm outperforms the traditional approach. As a benefit, secure communications can be guaranteed by using the proposed algorithm for the multiple input multiple output (MIMO) interference relay IoT network in the presence of an eavesdropper.