# A Survey on Intrusion Detection Systems for Fog and Cloud Computing
## 1 Introduction
### Cloud Computing Security
The methodology consists of numerous critical characteristics, such as excellent compatibility over different devices and the automated system that will easily automate updates, allowing it to easily adjust products to meet the client's needs and be accessible over a wide area covering many locations. In recent times, the SaaS model has succeeded due to the benefits it showcases and, therefore, is secured. This paper's main highlight is providing a solution to the security problem related to the SaaS to a cloud computing environment model. The proposed model also supports performing professional security audits. Therefore, this model will save money and time with a preferred level of security being desired in the cloud environment. The ability to pay for cloud-based systems and resources is an option and allows users to use the resources only at the required time. It is a good strategy to purchase and employ the most up-to-date technique. Elements that are vital to on-demand Infrastructure as a Service (IaaS) consist of customer isolation, multi-tenancy, and self-sustainability. However, cloud computing providers may adopt a level of control over users to create applications on top of the platform and security at the application level such as host, and intrusion prevention remains within the scope of providers. The service providers should offer appropriate assurances on the data's continued accessibility within apps. Three fundamental concepts are privacy, confidentiality, and obligations. These three are fundamental elements that contribute to privacy and confidentiality. Multitenancy is about sharing resources, where several users can share identical resources at various levels of the cloud domain, including the host level, the network level, and the application level. The services within cloud computing have different aspects that consist of the technology, including electronic health record websites, video sites, and data storage availability. There are two different application storage methods, namely, single cloud providers and many cloud providers. For example, a user's contents can be stored using a single cloud provider or many different cloud providers. Multitenancy implies the performance of sharing computational resources and storage as well as services and applications for different users. In the work in [3], it has been observed that multitenancy can be a leading cause of cybersecurity issues in fog and cloud-based environments. Multitenancy methods do not provide local privacy and require the location of the data to be controlled by users in the cloud-based environment. The multitenancy feature is designed to ensure sufficient resources are utilized and services and costs are available. This can result in the data of different users residing in the same location. The multitenancy in cloud service concentrates on a variety of requirements that can result in network security issues. These market elements include billing models, information governance, policy-driven enforcement, service levels, isolation for different user divisions. Elasticity is the property of adding and subtracting computing resources on-demand and releasing them when other resources are not in use. This can allow users the option to use the resources allocated previously, but it can represent a confidentiality threat in the cloud computing domain.