**7. Conclusions**

In this digital and modern era, technology is evolving every day. Due to the massive proliferation of technology, IoT and WSN play an important role in Industry 4.0 to develop smart applications, design networked data centers, and build autonomous smart industries. Data networks have been created and improved with the help of new and smart devices. In this systematic literature review, WSN and IoT network threats were analyzed and a descriptive comparative study was conducted. These networks are the main attack surfaces for attackers to draw meaningful patterns from system and user data. Wireless sensor networks (WSN) and the Internet of Things (IoT) have rapidly (and widely) evolved to meet the increasing demand for conventional application scenarios, such as plant automation and remote process control systems. These smart devices are also being used to improve the efficiency of existing networks and create new opportunities for automating and securing industrial processes. In this article, we explore seven research questions: (i) What are the contributions of WSN in IR4. 0? (ii) What are the contributions of IoT in IR 4.0? (iii) What are the types of WSN coverage areas for IR 4.0? (iv) What are the main types of network intrusions in WSN and IoT systems? (v) What are the main network security attacks in WSN and IoT? (vi) What are the major issues in IoT and WSN systems? (vii) What are the limitations and research gaps in the current work? The main purpose of the fourth industrial revolution with WSN and IoT explicitly shows that the evolutionary transition needs to be intensified and extended to include emerging research areas and intimidating technological challenges. This article covers all elements of WSN, from the design phase to the security requirements, from the implementation phase to the classification of the network, and from the difficulties and challenges of WSN. Future studies will address the problems in the coverage regions of wireless sensor networks and provide effective solutions to the existing problems and challenges in this area. The use and application of WSN and IoT in Industry 4.0 involves the processing of extracted data and the efficient and secure transmission of this data to a remote location.

**Author Contributions:** Conceptualization, M.M., M.R., and S.H.; data curation, S.H.; formal analysis, A.R.J.; funding acquisition, T.R.G.; investigation, A.R.J.; methodology, A.R.J.; project administration, J.C.-W.L. and T.R.G.; resources, G.S. and T.R.G.; software, A.R.J.; supervision, A.R.J. and J.C.-W.L.; validation, S.H. and M.M.; visualization, S.H. and M.R.; writing—review and editing, G.S., T.R.G., and M.R. All authors have read and agreed to the published version of the manuscript.

**Funding:** This paper is partially supported by the Western Norway University of Applied Sciences, Bergen, Norway.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Conflicts of Interest:** The authors declare no conflict of interest.
