1- Contiki OS + Cooja simulator
As we know, IoT will have various devices and can be divided into different networks. Thus, your security threat model needs to focus a certain level, but not all the levels including hardware, OS, network protocol, and application...The existing answers have clarify the good network simulators you can adopt (Cooja is a cross-level simulator but the others also can run with specific emulators like Qemu and etc).
SimpleIoTSimulator The InternetOfThings Simulator SimpleIoTSimulator™ is an easy to
use, IoT Sensor/device simulator that quickly creates test environments made up of thousands of sensors and gateways, all on just one computer.
64-bit RedHat Enterprise Linux (6.x or higher)
for more details:
3- NetSim v9
NetSim v9 (Latest Released Version, Feb 2016)
see this :
Research on Internet of Things(IOT) using NetSim
4- Internet of Things Simulator GUI Demo
to understand how its work :
5- AutoSIM IoT - Internet of Things Simulator
AutoSIM is the worlds first IoT simulator that can simulate 100+ million devices on a cluster of servers and supports 10 protocols below...
Automatski (Streamer & Chatterbox)
other custom protocols
see this :
Is gns3 simulator support internet of things?. Available from: https://www.researchgate.net/post/Is_gn ... _of_things [accessed Sep 3, 2017].