# A Survey on Intrusion Detection Systems for Fog and Cloud Computing
## 1 Introduction
### Cloud Computing Security  
The concept of cybersecurity is the assurance of safety from the activity of multiple entities (human and not), both internal and external, physically and in the cyberspace domain. Cybersecurity is classically characterized by the CIA triad:  
1. Confidentiality: This is the assurance that user information is kept private from unauthorized agents to access. 2. Integrity: This is the assurance of data remaining accurate and unmodified from the original state. 3. Availability: This assurance of data reliability is readily accessible to the authorized personnel upon request. To securely implement cloud computing technology, cybersecurity must be considered and applied to protect the information of the involved users. Keeping cybersecurity at the forefront of cloud-based environments aids in reducing the cyber threat risks and the assurance of compliance with rules and regulations set to ensure information security. A significant amount of Information Technology professionals is aware of cloud computing as a domain. Therefore, they should spend a significant amount of time understanding the security characteristics portrayed in cloud computing and related vulnerabilities. The increasing demands and adoption of computing can lead to improvements in the quality of services and user requirements. Web development has resulted in countless challenges, which can notably include the availability of massive data on the Internet--this has created an increase of servers with substantial storage capacity, enabling huge cloud storage capacity over vast geographical areas throughout the world. According to NIST, cloud computing is defined as a model that realizes the on-demand network accessibility, convenience, and ubiquity of computing resource configuration, including networks, storage, services, servers, and applications. They are provided and released quickly and do not require significant management or service provider interaction. The technology embedded in cloud computing covers five critical features: broad network access, a measured service, on-demand self-service, resource pooling, as well as the ability to have rapid elasticity. Service delivery models have different implementations, which make it complex to develop a standard security model that can be implementedby end-users of cloud computing. The service models include Infrastructure-as-a-Service (IaaS), Software-as-a-Service (SaaS), and Platform-as-a-Service (PaaS). There are four deployment models for cloud computing, classified as three basic and widely used deployment models: public, private, and hybrid clouds, and a less commonly employed model known as the community cloud. 1. A private cloud is deployed and managed within a single organization. 2. A public cloud is deployed and managed in a third-party organization. 3. A hybrid cloud consists of private and public cloud technologies. 4. A community cloud consists of sharing computing resources within multiple organizations and has the management operations completed by an in-house IT department or third party. There have been questions in the scientific community related to the significance of cloud computing. The management of these models can be extremely complicated, especially around meeting the cybersecurity needs around conflict and mitigation at the cloud level. The technology can require significant costs, including associated licenses with security solutions and resources, which are critical elements in achieving the standard and level of security needed--this can be a complex problem. Cloud providers need to pay close attention to the interests and requirements of end-users and seek suitable new security solutions to address users' concerns. The paper in [2] uses an approach that focuses on a method for Software-as-a-Service (SaaS) threat model relating to the cloud service providers. According to this study, the SaaS methodology is a dominant and widely used cloud model as it minimizes the investment and acquisition cost of the consumer and simplifies deployment.