  Internet of Things (IoT) is being considered as the growth engine for
industrial revolution 4.0. The combination of IoT, cloud computing and
healthcare can contribute in ensuring well-being of people. One important
challenge of IoT network is maintaining privacy and to overcome security
threats. This paper provides a systematic review of the security aspects of
IoT. Firstly, the application of IoT in industrial and medical service
scenarios are described, and the security threats are discussed for the
different layers of IoT healthcare architecture. Secondly, different types of
existing malware including spyware, viruses, worms, keyloggers, and trojan
horses are described in the context of IoT. Thirdly, some of the recent malware
attacks such as Mirai, echobot and reaper are discussed. Next, a comparative
discussion is presented on the effectiveness of different machine learning
algorithms in mitigating the security threats. It is found that the k-nearest
neighbor (kNN) machine learning algorithm exhibits excellent accuracy in
detecting malware. This paper also reviews different tools for ransomware
detection, classification and analysis. Finally, a discussion is presented on
the existing security issues, open challenges and possible future scopes in
ensuring IoT security.
