With recent advancements in technology, different devices that are used in our day-to-day lives are able to connect to internet, communicate and exchange messages with each other. This new paradigm is called “Internet of Things” and is providing services such as smart hospitals, smart city, home automation etc. “Internet of Things” has changed conventional small scale Vehicular Ad-hoc Network (VANET) to a highly scalable, manageable internet based “Internet of Vehicle” (IoV). IoV is a vehicular network model consisting of vehicles, users and other smart devices connected to network and aims to provide various safety as well as entertainment services. Vehicles in IoV system are equipped with different sensors that collect different types of data and send it to computation unit for computation and analysis, based on which directions and other information is sent to each vehicle. We present a model overview of IoV system in this paper. Security in IoV becomes of paramount importance as any system failure directly affects user safety. In this paper, we discuss security issues, various security attacks and their countermeasures from IoV perspective. We also propose an authentication mechanism for Vehicle-to-Infrastructure (V2I) communication in IoV.