## 2 DDoS Attack in IoT  
IoT networks are vulnerable to a wide range of security threats, including malware, ransomware, phishing attacks, and distributed denial of service (DDoS) attacks. Malware attacks can exploit vulnerabilities in IoT devices and can be used to gain unauthorized access to the device or to other parts of the network. Ransomware attacks involve the encryption of data on IoT devices and can be particularly damaging in IoT networks. Phishing attacks can be used to gain access to IoT devices or to launch other types of attacks, such as DDoS attacks. DDoS attacks in IoT networks are different from other IoT attacks in several ways. It can involve a large number of compromised devices, making them capable of generating massive amounts of traffic. This can make it more difficult to be detected and mitigated, which can cause widespread disruption to network services. Unlike other types of IoT attacks that may focus on stealing data or gaining control of devices, DDoS attacks in IoT networks can directly impact the availability of network services and devices, causing significant disruption to business operations or even critical infrastructure. DDoS attacks in IoT networks often involve the use of botnets, which are networks of compromised devices that can be controlled remotely by the attacker. Botnets are difficult to detect and can be used for other types of attacks, as well. IoT devices are often designed with limited security controls, making them vulnerable to exploitation by attackers. Thus, DDoS attacks present a significant threat to the IoT because IoT devices are often connected to the Internet and may not have adequate security measures in place. The goal of a DDoS attack is to disrupt the normal functioning of a network resource, such as an IoT device or server, by continuously flooding the system with traffic from fraudulent requests that overwhelm the system and prevent legitimate traffic from passing through. For example, a home webcam or home automation system could get malicious code from an attacker via IoT technology [23]. Attackers use trial and error techniques and these devices' built-in login and password lists to attempt to attack vulnerable devices. Due to outdated firmware, IoT devices are more vulnerable to hacking than desktops and smartphones. They are perfect targets for hackers to remotely influence because they are constantly \"online\". After becoming infected, these devices are added to botnets and start to take over the server or service that has been attacked [24]. The main potential damages of DDoS attacks on IoT devices are summarized in Table 1.  
In the literature, the study of DDoS attacks on the IoT environment is generally based on the IoT attack architectural surface areas [28]. Security issues are analyzed regarding the overall architecture of an IoT system [29]. Many experts and research organizations have proposed different IoT architectures. The perception layer, the network layer, and the application layer are regarded to be the three layers of traditional IoT architecture. However, the support or middleware layer--which sits between the network layer and the application layer--is later regarded as a crucial layer in light of the need for data processing and wise decision-making. Hence, Figure 1 presents the most widely used IoT architecture based on four layers with its adaptation to SDN paradigm: (1) perception layer, (2) networking layer, (3) middleware layer, and (4) application layer.