In recent years, vulnerable Intenet of Things (IoT) devices have engendered several distributed denial of service (DDoS) attacks owing to the generation of massive IoT botnets by various IoT malware such as Mirai, Persirai and among others. IoT devices are vulnerable owing to constrained memory and computation resources that restrict the implementation of complex security protocols and anti-malware programs. In recent times, there have been attempts to implement periodic Internet-Wide port scan (IWPS) to identify vulnerable IoT devices at each wireless local area network (WLAN). IoT WLAN standard such as IEEE 802.11ah has been designed with the objective of low power consumption and massive connectivity, but is constrained by its low network performance particularly on traditional scan traffic; thus it can result in security degradation. Hence, in this paper, we propose novel models for security analyses of IoT based on the network performance of IWPS over IEEE 802.11ah. The results verify that the network-Oblivious IWPS can degrade IoT security and increase risk.