Internet of Things(IoT) allows humans and everyday physical objects to interact and facilitates information sharing. Limited computational & memory capabilities, heterogeneous nature and lack of security mechanisms in IoT give rise to security and privacy concerns. Hence, vulnerable IoT devices lure attackers to exploit and turn them into a bot. A Botnet is a collection of these bots used to perform DDoS attacks later. Many IoT security breaches have been reported recently, which have disrupted the access to popular websites. In this paper, we analyzed the most recent Mirai malware, its exploitation techniques and proposed whitelisting based solution to prevent IoT Botnet from spreading and our experiments illustrates the successful blocking of Mirai malware