## 4 Main Security and Privacy Challenges
### Major Attacks and Countermeasures  
It is essential to note that vulnerabilities, threats, or security attacks can appear differently in different paradigms, and there exists no specific way of solving the various security issues. Thus, several designed models must be considered to safeguard a Cloud, Edge, or Fog computing system. This will help create a joint force of many reliable layer defense models [116]. Table 2 presents a detailed comparison of Cloud, Edge, and Fog paradigms based on a designated OSI model layer. Different attack examples were common to the three involved paradigms associated with the various layers. These identified security attacks and privacy leakages are matched to a specific proposed countermeasure. In some situations, the samecountermeasure of a particular paradigm can be applied to the other ones. However, due to the complexity of these paradigms or their ecosystem, this deployment of a single countermeasure is challenging. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Brief Description**} & \multirow{2}{*}{**Attack**} & \multicolumn{2}{c}{**Specifics of Paradigm/Main Proposed Countermeasures**} \\ \cline{3-5}  & & **Cloud** & **Edge** & **Fog** \\ \hline \hline \multirow{9}{*}{**Data inclined**} & & \multicolumn{2}{c}{Application} & \\  & & & monitoring is highly recommended. Web & Filtering mechanisms & \\  & & & Application Firewalls & and intrusion & HTTP-Redirect \\  & applications faces & Flood & (WAF), Anti-virus, privacy protection & detection systems [26]. & scheme [119]. \\  & & & management [118]. & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Attack specifics of paradigms and suggested countermeasures. As of now, end devices do not involve any established security measures. For this reason, during data transmission, security vulnerabilities are likely to be present. Some vulnerability research is underway to understand the different ways an end device or layer can face an attack. It is of significance that vulnerability research projects must be carried out extensively and in-depth when studying attacks and their aspects [141]. At each layer, we can deduce that security vulnerabilities are safeguarded differently. This attains the basic security demands such as confidentiality, authenticity, integrity, and not the least, availability. Cryptography is suggested for data confidentiality in stopping data leakages to illegitimate persons. Although cryptography turns out to offer better data confidentiality, it does need additional computation power, therefore causing latency. Users and end-devices have proximity to each other. For example, FNs pose some level of reach to individuals' data, especially where the information is generated. Data processed in FNs are significant security-wise due to their sensitivity more than data being processed in Cloud servers, thus requiring enhanced protection. Overall, Cloud, Edge, and Fog paradigms consist of applications, resources, and a massive quantity of end-devices within a given centralized or decentralized area, existing together and inter-communicating. Therefore, the huge potential for vulnerabilities in security and privacy does exist. One good way of screening systems for possible vulnerabilities is by auditing security standards. Vulnerabilities in any system might expressly grant attackers partial or full access to cause severe harm. If data are breached, it can expose critical information of individuals or organizations, and an attack can cause serious malfunctioning of an entire network and create disruptions.