Abstract : Nowadays, Internet of things (IoT) is one of the emerging domains which is growing exponentially. IoT is an idea that bridges the smart devices and let the devices to communicate with each other over the internet. IoT is an enormous system of associated gadgets – all of devices accumulate and share the information about how they are utilized and the situations in which they are working. IoT-based innovation will offer propelled dimensions of administrations and for all intents and purposes and it will change the manner in which individuals lead their day by day lives. IoT enhances machine-to-machine(M2M) communication that eliminates the need for human intervention. Smart homes, Smart Grids, Smart Cities, Earthquake detection, Healthcare, Smartphone detection, Radiation detection/hazardous gas detection, Water flow monitoring are some of the modern implementations in IoT. The future of IoT can only be assured if the security issues corresponding to IoT vulnerabilities and the mitigation techniques has been addressed. Since the IoT devices is been accessed remotely, there are many possibilities to flood the device and also results in many security issues. Hence it gives a path for the analysis of vulnerabilities in the IoT devices and evaluating the impact when the vulnerability is exploited. Based on the severity of the exploit, the mitigation techniques will be formulated. Many researchers have attempted to mention the security concerns specific to IoT layers and devices by implementing corresponding countermeasures. This paper presents a study of IoT security, IoT architecture, Security challenges, mitigation strategies for each layer of IoT, and the future work for IoT device security.