## 3 Q2: What Are the Challenges of the Current UIoT System
### Auditability
#### 3.4.3 Active Attacks  
The unauthorized attacker can alter, infuse, erase or destroy information in UIoT networks. The active attack can delete or modify the data during transmission and after transmission. Active attacks in UIoT are categorised into five categories: (1) Denial-of-service, (2) Message distortion, (3) Node tampering, (4) Message replay and (5) Masquerade attacks. The types of active attacks are classified under each layer of UIoT networks, such as a physical layer, data link layer, network layer, transport layer and application layer. Denial of service attacks is one of the deadliest active attacks and can cause a ton of damage. DoS attacks can be used at any layer of UIoT networks. DoS is an active attack that attempts to make assets out of reach to the authentic node. The attacker tries to block the authentic nodes from retrieving the services offered by the network [45]. Figure 6 shows the types of DoS attacks in UIoT. Node tampering: The UIoT nodes consist of hardware components such as a controller, battery, transmitter and receiver. In node tampering, the attacker can track and modify the software code of underwater nodes. Due to this, the software and hardware parts can be broken, which causes severe damage to the nodes in the UIoT environment. In effect, it causes network lifetime damages and data loss. _Message distortion_: In these attacks, the attacker can alter the data sent by one UIoT node to another. It can cause severe damages in case of emergency UIoT applications, e.g., message distortion in the naval application can break the security system. This could cause confusion by passing wrong information to the end-users. _Message Replay_: In these attacks, the attacker acts like the source node to send the same information already sent by the source node, or the attacker purposely delays transferring data by hacking. A message replay attack is also known as a play-back attack. _Masquerade_: In these attacks, the attacker uses the fake identity to steal the information from a legitimate node. A masquerade attack is a kind of privacy attack. _Jamming attack_: In these attacks, the malicious nodes frequently send the noise signal to disturb legitimate nodes in UIoT networks. Additionally, this attack can hack few special nodes inside the UIoT networks, such as root node, gateway, underwater cluster head, etc., which causes jamming in UIoT networks. In effect, it stops data transmission and gathering. Figure 7 shows the jamming attack where a malicious node continuously attacks the root node, disrupting the communication with the member node. Figure 6: Types of DoS attacks in the UIoT environment. Collision attack: This attack happens in the data-link layer of UIoT networks. A collision happens when two underwater nodes send packets at the same time. Hence, to avoid the collision in UIoT networks, the underwater nodes follow the data transmission rules, namely, that underwater nodes should not use the same time for data transmission. However, in a collision attack, the attacker will violate the rules and send the packets simultaneously. In effect, the UIoT networks need frequent retransmission and cause power loss. Exhaustion attack/battery-oriented attack: This attack aims to drain the total energy of underwater nodes in UIoT networks. For example, Figure 8 shows the battery-oriented attack of UIoT networks. Here, the malicious node sent a routing request (RREQ) message to node 0. In response, node 0 sent the routing response (RRES) message to the malicious node. Finally, the malicious node will continuously send the corrupted packets until node 0 becomes dead. In effect, it reduces network lifetime. _Node compromise attack_: An attacker can capture, break and compromise UIoT nodes to read or change information from memory. Moreover, what is terrible, is that the compromised nodes can penetrate into the network as authentic nodes to screen or disrupt it, which can prompt considerably more prominent harm.