On Friday October 21, 2016 there was a Distributed Denial of Service (DDoS) attack that took place on a DNS provider. Its objective was against major websites such as GitHub, Etsy, Twitter, Netflix, and Spotify. This paper is created in order to utilize the Free and Open Source Software (FOSS) available online to identify, classify and remove malware from a compromised system. Presenting an in-depth security analysis of Mirai botnet, a malware that convert devices running Linux into remotely controlled Bots, especially IoT devices, all the compromised systems were used as part of the Mirai botnet for performing large-scale network attacks. The methods presented in this article are generic and can be used as part of an incident response strategy to mitigate any malware of the same nature.