4.4.3. Intelligence Agencies

Intelligent agencies from other countries are involved in this type of attack. These agencies constantly seek to test the military architecture of other nations, including contemporary monitoring and covert political and military activities. To do so, they require many resources, from software to hardware, research, development, personnel, and finances. Because they have all these resources at their disposal, some agencies now pose a serious threat to economic and military espionage. Such organizations pose the greatest threat to networks and must be closely monitored to protect the nation's important assets [73].

#### *4.5. RQ5: Network Security Attack in IoT and WSN Layers*

Threats become more attractive and dangerous as technology increases. Although new security mechanisms are being developed, intruders can easily find other ways to attack systems. Table 8 explains the network security attacks in the IoT and WSN domains. The attacks are categorized according to the open system interconnection (OSI) layered point of view [74].


#### **Table 8.** Network Security Attacks on IoT and WSN Layers.

### 4.5.1. Denial of Service Attacks (DOS)

A Denial-of-service (DoS) attack is a malicious attack in which attackers make the victim's system unresponsive and difficult to reach for the legitimate user by making many requests to the expected URL than the server can handle [75,76]. DoS attacks typically occur when authenticated clients have not been granted access to the information or service [77]. A distributed denial of service (DDoS) attack is a type of DoS attack that uses multiple users or infected systems to attack a victim's system or to attack a website so that it becomes unresponsive. This attack also prevents the website from functioning properly and disrupts regular traffic. In WSN, a DDoS attack changes the routing protocol information DSR, resulting in a huge amount of unauthorized traffic and making the network/website unavailable. On the other hand, a low-rate denial-of-service (LDoS) attack is another type of DoS that penetrates the WSN's routing protocol, thus compromising the security and trust mechanisms. An LDoS attack is difficult to detect due to its non-stationary nature and low signal strength52. In this attack, illegitimate traffic affects the operational capability of a network. It causes severe outages and monetary losses.
