Internet of things connects all the smart devices with internet and gain more information in comparison with other systems. Since different types of objects are connected, privacy and security of the users must be ensured. Because of the decentralised nature, IoT is prone to different types of attacks which are either active or passive. Since internet is the main part of IoT, the security issues present in Internet will be available in the Internet of Things too. Distributed denial of service is a major threat of this type and a critical threat. It reduces the performance of the complete network even it breaks entire communication. For this reason many researches have been made in this area to detect Distributed Denial of Service attack. Entropy-based approaches to identify DDoS attacks in the internet of things are discussed in this research. This new approach is based on the GRJE method, which stands for generalised Renyi joint entropy. Renyi joint entropy is used in the suggested approach to analyse network traffic flow. The suggested method is put into practise and evaluated against other methods based on a few factors. Results from an analysis of the suggested system's effectiveness in NS2 are reported in this study.