Wireless technology is utilized by various Internet of Things (IoT) devices, such as smartphones, drones, and cameras, to establish multiple inter-device connections simultaneously. The flexibility of wireless networks allows users to create IoT-based ad-hoc networks on demand. This connectivity enables linking hundreds to thousands of people, leading to significant enhancements in productivity and profitability. However, the flexibility of the IoT network also introduces a range of threats that require attention. The primary research methodology employed in this study was simulation to investigate and identify existing vulnerabilities or loopholes in the transport layer of IoT networks that use the ad-hoc on-demand distance vector (AODV) routing protocol. The simulation software utilized was NetSim 12.02, which is based on the Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 standard. We conducted simulations of synchronization (SYN) flood attacks on IoT networks by exploiting vulnerabilities in the underlying protocol. The tests and data collection for this study were conducted using the simulation software. The research demonstrates that the transport layer of the IoT network, when utilizing the AODV protocol, can be compromised to launch a SYN-flood attack, resulting in severe performance degradation of the system. The results demonstrate that SYN-flood attack nodes result in a decrease in throughput ranging from 9.1% to 17.79%, an increase in delay ranging from 1.08% to 3.26%, and an increase in network jitter ranging from 15.4% to 22.88%. These findings can assist IoT network administrators in better planning and implementing preventive measures against SYN flood attacks on IoT networks that utilize the AODV protocol.