In today’s world Internet of Things (IoT) devices can be found everywhere in homes, offices, agriculture, healthcare, insurance, transportation etc. These devices have brought significant changes in our daily lives, society and industry. But securing these IOT devices has become utmost important for manufacturers as well as their consumers. Because human factors are intertwined with IoT infrastructure, it's critical to think about data security and device functionality. Traditional security methods can’t be applied to these devices due to their heterogeneity and resource constraints. Distributed Denial of Service (DDoS), Man In The Middle (MITM), and replay attacks are some of the most common types of attacks. This literature review paper intends to analyze recent research in IOT security from 2018 to 2021. Goal of this paper is to provide researchers information about IoT security research, challenges and countermeasures, open issues, datasets and simulation models used for IoT Security.

KEYWORDS: Internet of Things (IoT), Distributed Denial of Service (DDoS), Man in The Middle (MITM).