A Comprehensive IoT Attacks Survey based on a Building-blocked Reference Model <s> II. IOT REFERENCE MODELS <s> This paper addresses the Internet of Things. Main enabling factor of this promising paradigm is the integration of several technologies and communications solutions. Identification and tracking technologies, wired and wireless sensor and actuator networks, enhanced communication protocols (shared with the Next Generation Internet), and distributed intelligence for smart objects are just the most relevant. As one can easily imagine, any serious contribution to the advance of the Internet of Things must necessarily be the result of synergetic activities conducted in different fields of knowledge, such as telecommunications, informatics, electronics and social science. In such a complex scenario, this survey is directed to those who want to approach this complex discipline and contribute to its development. Different visions of this Internet of Things paradigm are reported and enabling technologies reviewed. What emerges is that still major issues shall be faced by the research community. The most relevant among them are addressed in details. <s> BIB001 </s> A Comprehensive IoT Attacks Survey based on a Building-blocked Reference Model <s> II. IOT REFERENCE MODELS <s> Ubiquitous sensing enabled by Wireless Sensor Network (WSN) technologies cuts across many areas of modern day living. This offers the ability to measure, infer and understand environmental indicators, from delicate ecologies and natural resources to urban environments. The proliferation of these devices in a communicating-actuating network creates the Internet of Things (IoT), wherein sensors and actuators blend seamlessly with the environment around us, and the information is shared across platforms in order to develop a common operating picture (COP). Fueled by the recent adaptation of a variety of enabling wireless technologies such as RFID tags and embedded sensor and actuator nodes, the IoT has stepped out of its infancy and is the next revolutionary technology in transforming the Internet into a fully integrated Future Internet. As we move from www (static pages web) to web2 (social networking web) to web3 (ubiquitous computing web), the need for data-on-demand using sophisticated intuitive queries increases significantly. This paper presents a Cloud centric vision for worldwide implementation of Internet of Things. The key enabling technologies and application domains that are likely to drive IoT research in the near future are discussed. A Cloud implementation using Aneka, which is based on interaction of private and public Clouds is presented. We conclude our IoT vision by expanding on the need for convergence of WSN, the Internet and distributed computing directed at technological research community. <s> BIB002 </s> A Comprehensive IoT Attacks Survey based on a Building-blocked Reference Model <s> II. IOT REFERENCE MODELS <s> IoT (Internet of Things) diversifies the future Internet, and has drawn much attention. As more and more gadgets (i.e. Things) connected to the Internet, the huge amount of data exchanged has reached an unprecedented level. As sensitive and private information exchanged between things, privacy becomes a major concern. Among many important issues, scalability, transparency, and reliability are considered as new challenges that differentiate IoT from the conventional Internet. In this paper, we enumerate the IoT communication scenarios and investigate the threats to the large-scale, unreliable, pervasive computing environment. To cope with these new challenges, the conventional security architecture will be revisited. In particular, various authentication schemes will be evaluated to ensure the confidentiality and integrity of the exchanged data. <s> BIB003 </s> A Comprehensive IoT Attacks Survey based on a Building-blocked Reference Model <s> II. IOT REFERENCE MODELS <s> The rapid development of technology currently revolves significantly around Internet of Things (IoT) and expected to play an important role in coming days. IoT has become the focus of attention for many researchers to discover issues and challenges that related to its design and architecture. One of the many significant issues is the multitude of languages, protocols and standards, as well as the lack of agreement on which it works best for individual layers of the IoT. It does not have a single platform of standardization; it is changed due to the heterogeneity of connected things. This paper discusses Lack of Standardization issues, challenges and review existing state of the art standards to highlight and overcome it by presenting some technical solutions. <s> BIB004
The state-of-the-art has shown that there is a lack of standardized approaches for understating and modeling IoT vision in many aspects BIB004 . First, differentiating between an IoT system and a non-IoT system is not absolutely clear. It is worth noting that not every system is the IoT system. In fact, when data is created under the control of objects or entities and forwarded or sent across a network, it can be considered as the IoT system  . Second, identifying precisely IoT assets and its components is very confusing due to the complexity of IoT ecosystem, varying from physical objects placed in the environments until their data and applications resided in the cloud. As a result of this complexity, they are susceptible to many attacks and threats BIB003 . Third, IoT umbrella covers different applications, development stages or cycles, middleware, fog computing, software platfrom , protocols and hardware platforms. That said, it lacks a common ground to be understood by researchers or even IoT developers  . Motivated by above mentioned aspects, handful of papers have been proposed to establish a common ground of understanding IoT paradigm known as IoT reference models, the most dominant of which are the following: 1) The three-layer model as shown in Fig. 1 represents IoT system as an extension to wireless sensor networks (WSN) BIB002 . In other words, it can be considered as an integration of WSNs and cloud severs providing several services to the users. 2) The five-layer model as depicted in Fig. 2 is relatively more structured suggested to ease the communications among several components of IoT system by dividing the complex system into a well-defined part BIB001 , compared to the previous one. 3 ) The seven-layer developed by Cisco as shown in Fig.  3 extends both the three-layer and the five-layer models, trying to create a comprehensive and agreeable IoT reference model  . Its capability of standardization makes it ideal for IoT system. Despite the simplicity of RMs mentioned above which breaks down the complexity of IoT ecosystem into different layers, they lack the required building blocks for their layers. An IoT building block is an essential unit or an enabler technology on which IoT system is constructed. In the context of IoT vision, building blocks are nowadays receiving more attention to provide a better understanding of IoT. Authors in  have described different building blocks. The most important ones are the identification, sensing, and communication. To this end, we propose a four-layered reference model based on building blocks strategy as shown in Fig. 4 , the main contributions of such model are the following: First, the great contribution we intend to produce lies in merging each layer of IoT RMs with the required building blocks. This kind of combination would greatly help IoT stakeholders, paving the road for precisely identifying IoT components and assets. Second, we believe that building blocks would lead to a huge change in the mentality of security analysts who used to address security issues as a whole for each layer, making them address security issues of specific enablers technologies at each layer. Third, equipped with a set of building blocks at each layer, it introduces a new classification of IoT assets composed of four main components, hardware components, protocols, data at rest, and software including operating systems, firmware, and applications. These components will be used as a staring point in our attack model proposed in Section IV. The proposed IoT reference model classifies building blocks broadly into three categories, protocols, hardware components, and software. In general, protocols fall under five building blocks in our model: connectivity, routing and networking, service discovery, communication, and web service and web servers protocols. Hardware components consists of two main building blocks: 1) sensing, which includes sensors, actuators, and RFID; and 2) hardware platforms or microcontrollers, which include different types of micro-controllers. Finally, software components are composed of four building blocks: operating systems, fog computing, middle-ware, and could solutions. Despite the difference in the number of layers in both our model and Cisco reference models, they have the same IoT components. To validate that our reference model have covered the most important IoT components, we compare it with Cisco's reference model. Unlike Cisco's model, its first layer is specialized for physical devices, perception level in our model includes not only physical objects but also connectivity technologies represented in different layers in Cisco's model. By observing Fig. 3 , it is obvious that layer 1 and layer 2 in Cisco's model have been merged into one layer in our reference model shown in Fig. 4 . In contrast, the layer 3 in Cisco's model has been divided into two layers (2 and 3) in our proposed reference model. Finally, our last top layer, the cloud layer, includes four layers of Cisco model, starting from layer 4(Data accumulation) until the last one known as users and data centers. It is worth noting that this paper is not meant to give a detailed explanation of the previous IoT reference models, because they are beyond the scope of this work. Each layer, in our model, is associated with specific tasks and functions and the data movement is often bidirectional, either from the cloud layer to the perception layer in the controlling mode or from www.ijacsa.thesai.org Fig. 1 . Three-layer model BIB002 . Fig. 2 . Five-layer model BIB001 . Fig. 3 . CISCO's seven-layer model  . the perception layer to the cloud in the monitoring mode.