###### Abstract
[8] centralized on the security of IoT communication protocols, includes physical and medium access control (MAC) layers, IPv6 over low power wireless personal area network (6 LoWPAN), routing protocol for low power and lossy networks (RPL). [PERSON] et al. [9] focus on the security of IoT and WSN communication protocols and their attack-resistant solutions. Subsequently, [PERSON] et al. [10] gave a detailed security analysis of IoT routing protocols, particularly in low-power and lossy networks (LLN). Then, [PERSON] et al. [11] briefly discussed IoT security from a data-centric perspective. [PERSON] et al. [12] directed to analyze consumer IoT devices. [PERSON] et al. [13] and [PERSON] et al. [18] review the adaptability of blockchain in securing IoT applications and architecture. [PERSON] et al. [14] focus on discussing the security of IoT applications. [PERSON] et al. [15] and [PERSON] and [PERSON] [16] directed to review the IoT security from a programming platform and code-level perspective. [PERSON] et al. [17] discuss the relationship between deep learning, IoT security and big data technologies. [PERSON] et al. [19] gave a general review of threat models and attack paths of IoT. Recent IIoT surveys have primarily focused on the general IoT domain rather than the IIoT domain. They either provided a general overview of IoT security [1, 2, 3, 4, 5, 10, 11, 19], or a detailed security analysis limited to specific IoT technologies or a particular layer of IoT architecture [6, 7, 8, 9, 12, 15, 16]. In addition, multiple surveys focused on exploring the relationship between IoT security and blockchain technologies [13, 14, 17, 18]. Survey directions have lately been directed to be hammered down in the IIoT domain [20, 21, 22, 23, 24]. Deep learning in IIoT threat detection [20, 22] and decentralised blockchain technologies [22, 23] are the focus of these IIoT security surveys. However, none of them performs comprehensive security analysis on IIoT architecture and its recent industry solutions. Whether these deployed security solutions in the industry are still adequate to be adapted to secure IIoT architecture are questionable. The contributions of this article are:  
* The difference between conventional systems and IIoT security concerns are summarized. Decentralized security approaches with high scalability, high interoperability, lightweight, and secure data processing have urged to address the high heterogeneity of \"things,\" high volume, and variety of collected sensor data, as opposed to conventional security systems focused on a centralized approach. * Unlike recent IIoT architectures [24, 25, 26, 27] that (i) focused on specific industries: aviation industry [25] and smart manufacturing [27], and (ii) targeted on particular technologies: M2M communication [24], green-aware multi-task scheduling [26] and 5G technology [27], we generalized the IIoT architecture into a four-layer architecture to cope with a wide of industry technologies and standards. * Subsequently, we classify the recent IIoT technologies and standards into the proposed four-layer IIoT architecture
* The IIoT security requirements are further defined with the CIA+ model, includes confidentially(C), integrity(I), authentication(A), authorization and access control (A) and availability (A). * A comprehensive end-to-end security analysis was conducted based on the defined IIoT CIA+ model. Subsequently, a fine-grained review on recent industry technologies and standards in each layer of the proposed IIoT architecture. The identified security risks and threats of these industry technologies, their deployed security countermeasures and future research works are summarized
* Lastly, we enumerate the open security challenges of IIoT and future research opportunities. The rest of this article is organized as follows. Section 2 investigate the characteristic of IIoT, highlights and report the difference between conventional systems and IIoT security concerns.