## 3 Q2: What Are the Challenges of the Current UIoT System
### Auditability
#### 3.4.3 Active Attacks
An attacker can find the network by checking the power of the acoustic signal and capturing them. More regrettable, is that xfwithout a trace of hack-confirmation equipment or other security systems, the attacker can undoubtedly break and compromise them to inspect private information (e.g., the secret key, the encryption algorithm, the trust esteem) and alter this information in the inward memory. Additionally, the compromised node can be penetrated into the network as an actual node to screen it or perform persistent attacks. _Sybil attack_: The Sybil attack is a type of routing attack. In this case, the attacker uses a fake identity to steal the information while routing. Figure 9 shows that the attacker can  
Figure 8: Battery-oriented attack. Figure 7: Jamming attack in the UIoT environment. locate any place in UIoT networks and use multiple identities to mislead routing. In effect, it causes packet loss or transmission delay [46; 47; 48]. Wormhole attack: An attacker uses two malicious nodes to tunnel traffic through the UIoT networks in a wormhole attack [49; 50; 51; 52]. The two plotting nodes capture packets at one end and block them at another end. Wormhole attacks can make fake neighbor associations and give the probability of an alternate path for routing. Figure 10 explains how a wormhole attack occurs, causing a breach in the communication link, only because it looks like the distance of the wormhole node is shorter than legitimate nodes. Unfairness: This is a type of DoS attack. The attacker aims to reduce the performance of the legitimate nodes instead of completely blocking them from data transmission. In effect, it can create transmission delay in UIoT networks. _Hello flooding attack_: In a UIoT environment, every node will send HELLO packets to identify its neighbor node. In a hello flooding attack, the adversary node in a UIoT network will send numerous HELLO packets to legitimate nodes to exhaust their battery power. In this case, the adversary node will convince the legitimate node by transmitting the signal with high intensity. Therefore, the legitimate node will assume the adversary node as the neighbor node and transmit data. In effect, it causes power failure and reduces the network lifetime. Figure 11 shows that the malicious node sends HELLO packets with high signal strength to attract the legitimate nodes in UIoT networks [53]. Figure 10: Wormhole attack in the UIoT environment. Figure 9: Sybil attack in UIoT environment. _Selective forwarding_: In these attacks, the malicious node is located nearby the gateway of UIoT networks. When some packets are detected, the legitimate nodes will find a new route for transmitting the data to the gateway. As shown in Figure 12a, the malicious node can selectively drop some packets before reaching the destination in this attack. In effect, it causes packet loss in UIoT networks. _Blackhole attack_: In these attacks, the malicious node acts as the cluster head or gateway to drop the packets while routing. Figure 12b shows that the malicious node can blackhole by modifying or dropping the packets routed from legitimate nodes. The dropped packets are referred to as black hole attacks in UIoT networks. _Gateway block attack_: In this attack, the malicious node is located near the gateway and blocks all the data transferred from legitimate nodes to the gateway. In this case, the attacker manages to steal all the routing information sent to the gateway as the destination. In effect, it causes complete packet loss. Therefore, a gateway block attack is referred to as the main threat in UIoT networks. _Misdirection attack_: In this attack, the malicious node can be located anywhere in the UIoT network and track the routing path to change the route to the malicious node. In effect, this attack causes packet loss or data transmission delay. _Homing attack_: The malicious node observes the traffic in UIoT networks and attacks the most special nodes in UIoT networks, such as cluster head and gateway.