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  1. A STUDY ON CLOUD COMPUTING SECURITY SVTH: Đỗ Chí Bằng, Nguyễn Thị Ninh Thuận GVHD: ThS Hoàng Thị Kiều Hoa Tóm tắt - Bảo mật điện toán đám mây là một lĩnh vực nghiên cứu sâu rộng với nhiều mối quan tâm khác nhau ở nhiều khía cạnh. Trong khi lợi ích của điện toán đám mây và các dịch vụ đám mây có thể dễ dàng nhận thấy, các vấn đề về quyền riêng tư và bảo mật của công nghệ này luôn được chú trọng. Bài báo này nhằm mục đích xác định các vấn đề bảo mật và giải pháp của chúng trong việc sử dụng các dịch vụ điện toán đám mây. Và đây sẽ là tài liệu tham khảo cho bất kỳ ai cần cái nhìn tổng quan về các yếu tố rủi ro và các giải pháp khả thi trong môi trường đám mây. Abstract - Cloud computing security is an extensive field of research with various concerns in many aspects. While the benefits of cloud computing and cloud services are easily noticeable, the privacy and security problems of this technology has always been concentrated on. This paper aim to identify the security issues and their solutions in using cloud computing services. And this would serve as a reference for anyone in need of an overview on the risks factors and possible solutions in a cloud environment. Key words: Privacy, Cloud computing, Cloud Consumer, Cloud Service Provider, Cloud User, Security. I. Introduction about cloud computing security Since its popularization by Amazon’s Elastic Computer Cloud (EC2) in 2006, cloud computing has been heavily focused on and developed by many other information Enterprises such as Dell, Microsoft, Google…During 2020, the COVID-19 pandemic has affected the cloud computing market exponentially. The demand for Software-as-a-Service (SaaS) surged due to the adaptation of work from home model in some enterprises. Video conferencing programs using cloud computing such as Google Hangouts, Zoom, WeChat Work, Tencent Meeting, Cisco Webex,… has experienced over three times in new user registration number (Marketsandmarkets, 2020). Moreover, streaming platforms such as Netflix, Twitch, Hulu, Amazon, Disney+, Youtube… has also undergone a significant increase in demand due to country lockdowns causing most of the people to stay indoors. Thus, Video on Demand (VoD) which uses the cloud is vital and has remarkably raised the demand for Infrastructure as a Service (IaaS). According to Research and Market, the global cloud computing market size in 2020 is 371.4 billion USD and should reach 832.1 billion by 2025. This clearly shows the importance of cloud computing during this digital age. With new technology comes new risks and issues, the problem of Cloud security has become a major challenge of cloud computing. To prevent such issue, many solutions are 131
  2. introduced by IT workers (Subashini & Kavitha, 2011). In this paper, Cloud computing basic information will be mentioned, following with the security risks cloud computing possesses and then possible solutions will be presented before we conclude the paper. II. Cloud computing, Cloud security risks and solution A. Definition 1. Cloud computing Cloud computing or cloud is referred to deliver possibly on-demand network, which operates from applications to store data and processing power. People access to cloud computing through the Internet and have a pay for their business. With an invention of cloud computing, users no longer spend a huge amount of money getting their own computing infrastructure of data centers, instead, they might rent cloud computing (CC) provider applications to store their data on the Internet. In addition, the benefit of cloud computing is that we can use our information every time and everywhere on the Internet without carrying a hardware disk or settling work on computing infrastructure at the office (Steve R., 2018). Therefore, since the beginning of cloud computing, it has been attracting many attention in both the industrial field and the academic field because of its convenience (M. Sadiku & S. Musa & O. Momoh, 2014). Clouds nowadays are so familiar for the people in their daily life, which most of which is not recognized by the users. Some typical examples of cloud computing are iCloud, Office 365, Google Drive or Dropbox,… Certainly, cloud computing is a big leap for IT (Information of Technology) as this new-born network model has drastically changed the way we conceive networking today. 132
  3. The cloud system can be dived into front-end and backend. The frontend helps the user to access a data stored in the cloud using an internet browser or a cloud computing software while the backend comprise of servers, computers, databases, and central servers - the primary component of cloud computing, responsible for securely storing data and information. Fig. 1. Public Cloud Adoption for Enterprises 2. Security information Security information is a common problem for all operational system, security within cloud computing happens expectably (2015). The term “cloud security” refers to discipline of policies, controls, procedures and technologies for protecting cloud based-system, applications, data and information. These used solutions are to protect data, regulatory fidelity and importantly clients’ privacy while backup rules for individual users and devices as well. Running cloud security shall be a co-operation between the cloud owner and solution provider to get the most effective cloud protection (Cyber Edu, 2020). The measures for security issue are flexible depending on the various types of cloud computing, with an attempt to bring the best solutions for each characteristic (Mall & Grance, 2011). Clouds are deployed using varying deployment methods which are broken into three primary types of cloud environments: public, private, hybrid and community clouds (2015). 133
  4. 3. Types of cloud computing Cloud computing Public Private Hybrid Community cloud cloud cloud cloud Fig. 2. Cloud computing deployment method 3.1 Public cloud This term is easily understood that the service is hosted by third-party cloud service provider such as a government, organization or companies and is allowed to be used freely by the public (Mall & Grance, 2011). The management and maintenance of a public cloud is entirely dependent on this third-party provider, with the responsibility of keeping the data of their customers safe and secure. One of the obvious benefits of using a public cloud is the reduction of maintenance cost for a data center. 3.2 Private cloud A private cloud is ordinarily involved and accessible to only an organization, the provider is its own organization or third-party (Mall & Grance, 2011). This is known as an internal or enterprise cloud, typically located on a company’s data center, or its intranet. One special feature of this type is that they are unlikelihood to approach violations, social engineering and other exploits (Beyond Trust, 2020). However, opposite to the public cloud, a private cloud requires management, maintenance and updating of data centers and in the long run, the costs of replacing old servers would be moderately high. 3.3 Hybrid cloud Hybrid cloud is described as a combination of public and private clouds which all remain unique components from both types (Mall & Grance, 2011). The users have more right to examine their data than usually utilizing public cloud. On the other hand, they still may access to scalability and the benefits as wanted (Beyond Trust, 2020). According to a report in 2019, enterprises using hybrid cloud grew from 58% to 51% in a year. This is due to its combined advantages between public and private clouds such as improvement of security, risk management and reduction of costs. 3.4 Community cloud 134
  5. Community cloud is an infrastructure for a community from different organizations sharing common perception. This is operated by organization themselves or third-party. Additionally, this service may be setup either inside or outside the CSP ( Cloud Service Provider) (Srinivasan, Sarukesi, Rodrigues, Manoj, & Revathy, 2012). Taking advantage of that, the cloud users pursue exploiting economies which reducing cost associated with private and hybrid clouds, and the risks of public clouds (Boampong & Wahsheh, 2012). 4. Service Models While considering cloud security from cloud environments, the cloud-based security applies to service model environments (Beyond Trust, 2020). Service models or SPI (software, platform and infrastructure) provide various services to the users (Ali, Mazhar, Samee U. Khan, & Athanasios V. Vasilakos, 2015), moreover, each deployment characteristic can use service model as well (Cloud Security Alliance, 2011). Service Model IaaS PaaS SaaS Fig. 3. Cloud computing Service Model 4.1 Infrastructure as a Service Infrastructure as a Service or “IaaS” is defined as a service offered infrastructure solutions. One essential advantage of this service is the ability of allowing the costumer to pay base on how much storage they use and to freely customize after hiring the infrastructure (Srinivasan, Sarukesi, Rodrigues, Manoj, & Revathy, 2012). The responsibility of managing the infrastructure belongs to the provider. This service, known for its evolutionary hosting service, does not depend on any long term commitment and grant the users freedom of managing the resources on demand. Similar to a data center, the host will supply the network access, routing services and storage as well as offering the hardware, administrative services, and the platform for the user to run their application. 4.2 Platform as a Service 135
  6. This service provides tools and computing infrastructure that can be used when building, running web applications and distribution (Srinivasan, Sarukesi, Rodrigues, Manoj, & Revathy, 2012). PaaS (Platform as a Service) fundamentally backups developers, develop team and operations to establish a program (Beyond Trust, 2020). This means the platform is provided while the customer can upload, run their codes and start their application. 4.3 Software as a Service Abbreviated to “SaaS”, this service consists of instant applications and the underlying database hosted by a third-party, delivered as a software services over a web browser (Srinivasan, Sarukesi, Rodrigues, Manoj, & Revathy, 2012). One thing taken into consideration is that SaaS makes no plea for deploying applications on end-user devices. Furthermore, any customers can access to the web browser and utilize its information (Beyond Trust, 2020). All the responsibility lies on the provider, while the costumer buy for the finished product and application. B. The issues in cloud computing security and solutions The development speed of cloud computing is astonishing, which leads to an increasing number of organizations and individuals utilizing its beneficial functions (A.Rot., 2017). However, it is unavoidable that several risks are able to emerge from this new technology and one of the most significant obstacles that needs to be dealt with is security risk (KPMG’s 2010, cloud computing survey). According to K.Djemame, risks of cloud computing are the unwanted incidents and consequences for particular assets and the level of the risks is determined by the value of the raised or the possibility of that risks. Since the cloud is a brand-new computing paradigm, the issues regarding its security will be focused on by two parties: the Cloud Consumer and the Cloud Service Provider (CSP). Moving confidential data and critical application away from the data centers is literally a risky decision for organizations. Therefore, to extenuate these concerns, the CSP must assure that the users can have security and privacy controls over their applications and services. Furthermore, they are required to bring evidence to prove that the organization of the consumer is greatly secured, meeting their service level of agreement from the customers (Rittinghouse, J and Ransome, J, 2009). To achieve a broad overview about risks of cloud security, this research will focus on both Cloud consumer and CSP orientation of cloud security. There are 5 primary categories of security risk: Physical Security, Data Security & Privacy, Technological, Organizational and Compliance & Audit. Some of the most commonly faced problems, referred to as the main risks are the first three categories due to the majority of customers using cloud services for business purposes only (A.Rot., 2017). 136
  7. 1.Risks and solutions from Cloud Provider Perspective 1.1 Physical Security Physical security is designed to avoid unauthorized access to the cloud facilities, equipment and resources and to prevent personnel and properties from attackers such as espionage, theft, or terrorist attacks (“Field Manual 3-19.30: Physical Security.” Headquarters, United States Department of Army, 2001). In detail, CSP deals with the risks in data location and data center which means they are responsible for guaranteeing the secure operation of the cloud data center in order to provide an ensured physical location for customer’s data (Julisch, K and Hall, M., 2010). Moreover, secure operation of infrastructures including servers, networks and storage devices is also required. This can be achieved by having the appropriate physical security of interdependent systems, namely staff training, physical location security, network firewalls for denial of service attacks (DoS), and other deterrent systems. Addressing this problem is crucial since the physical system being vulnerable will lead to attackers or hackers able to stole the entire server, even with the protection of firewalls and encryption (Julisch, K and hall, M., 2010). Moreover, the providers bear both responsibility for storing and processing data within jurisdictions and complying with privacy regulations as well (Kumar, Ashish, 2012). 1.2. Data Security and Privacy The method of maintaining confidential and secure data for users from unauthorized approach as well as anonymous or unintentional changes is truly not an easy task. One major issue in securing and privatizing user data is the lack of the overall control of it (Chen & Zhao, 2012). Basically, when providing users with cloud services, it can be divided into three types of services which are IaaS, PaaS and SaaS. Noticeably all of the services have their data stored in the cloud, rather than on a local hard drive for example the Amazon Simple Storage Service. Thus, to protect the data in the cloud, encryption is utilized to minimize the risk of 137
  8. private data becoming public (Behl & Behl, 2012). For further information, CSP assure data integrity, privacy and availability by proving encryption schema and scheduled data backups (Harauz, J, Kauifman, M and Potter, B., 2009). They also adopt added solutions to ensure data security that involve the strong technological encryption and reinforce authorization to control customer’s access to data (Subashini, S and Kavitha, .V, 2011). Providers hold more responsible for the privacy and security of data and applications services in public than in private clouds (Takabi, H and Joshi, James.B.D, 2010). However, the key issue lies on management which ideally belongs to the owners. Due to the shortage of expertise needed to manage their encryption, CSP has to solve this problems. Unfortunately, managing a huge number of keys for service provider is a strenuous challenge to handle (Chen & Zhao, 2012 & Rahul, S, Sharda and Dr. Rai, 2013). The tasks for providers are processing, transferring and storing data (Hashizume, K., Rosado, D.G, Medina, E.F and Fernandez, E., 2013). Aside from these, users have no permission to modify physical security system in data center whose task is for the infrastructure provider. It may leads to a security breach as there can be no absolute certainty that the data is interfered with or not. This concern is legitimate due to the fact that the CSP is the only party that can control the security settings remotely (Reddy, V.K., Thirumala, R.B, Dr. Reddy, L.S.S and Sai Kiran, 2013). For storing data in PaaS or SaaS, encryption seems to not be a potential solution because the data which are stored in applications are not feasible to be decrypted and encrypted in each computing tasks (Chen & Zhao, 2012). Therefore, measure similar to encryption is not usually considered to tackle security problems though it is possible to perform some computing tasks, it is unsuitable for most model services (Tari, 2014). Cloud databases 2018 Encrypted 49% 51% Unencrypted Fig. 4. Cloud Databases in 2018 Identity and Access Management (IAM): IAM helps the providers to increase operational efficiency, regulatory obedience 138
  9. through managing core security issues, automatic provisioning, authentic and authorized services. In Dervki’s study, he suggested that the concerns are solved by exerting various techniques (such as single sign-on, federated identity of users, controlled list, guiding based service, etc.) (Khajeh- Hosseini, A, Ian Sommerville, Bogaeert, J and Teregowda, P., 2011). To deny unauthorized access, it is advised that the CSP should implement strict regulatory mechanism, control and monitor administrative access (Harauz, J, Kauifman, M and Potter, B., 2009). In terms of the issue of jurisdiction and privacy in general, it also raises several concerns since the users’ confidential data may be outsourced to cloud, including secure and reliable data access which is certainly critical. This will significantly affect the policy of cloud providers (Pal, D., Krishna, R., Srivastava, P. and Kumar, S., 2012). The measure is to encrypt data in varying manner, and allow corresponding decryption to only authorized customers, which leads to some drawbacks in loss and scalability (Ren, K., wang, C. and Wang, Q, 2012). Multi-tenancy: This is a crucial attribution of the cloud by adding the use of underlying hardware resources and letting adequate resource to provision. Multi-tenancy security is a drastic challenge for the CSP (Ren, K., Wang, C. and Wang, Q., 2012). The CSP have a duty of protecting isolated boundary for each user at both physical and application levels (Subashini, S and Kavitha, V., 2011). Most of the service providers employ virtualization to maximize the volume of using hardware (Pearson, S. and Benameur, A., 2010). At once, attackers take this advantage of approaching the host to extract information from the database (Hashizume, K., Rosado, D.G, Medina, E.F and Fernandez, 2013). Certainly, the providers should add some mechanism for guarantee of data isolation (Ayala, L.C., Vega, M. and Vagas, L.M., 2013). - Data Availability and Backup: It is a tough mission for the CSP to maintain data availability and backup in the cloud since the data is managed distantly (Pearson, S. and Benameur, A., 2010). In cloud environments, there are multiple threats, comprising the availability of cloud computing services (Chen & Zhao, 2012). This must be solved by an agreement between users and CSP to specification relating to system availability (Zissis & Lekkas, 2012). With availability, it is important to keep a local backup that user stores in the cloud. Unavoidably, security against data loss occurs from the utility of backups. When a risk occurs, both user and data owner should be held responsible, with no relation to the CSP. For CSP, they improve the technology to support reliable backups, assure that backups are being operated and stored in safe manner. They solely have a duty when faulty backups happen unexpectedly (Khalil, Khreishah, Bouktif, & Ahmad, 2013). 139
  10. 1.3. Technical risks: Technical risks are the failures in the technologies and services provided the CSP. These types of threats in the cloud consists of resource sharing isolation problems, malicious attacks associated with portability and inter-operability (Rana, S. and Joshi, P. K, 2012). These issues emerge due to the poor maintenance of hardware, unresponsive system, and mitigation of availability and hardware failure (Djememe, K, Armstrong, D., 2011). With portability in the cloud, inter-operability is for incompatibilities among CSP platforms. The suggested solution is using the cloud middleware (or public/ private cloud) which acts as an intermediary between networks and applications much like between server and customers. Another risk is service interruption at the provider side which results in outages, inaccessible services or loss of data. In the authors’ point of view, they recommended using multiple cloud providers and monitor applications outside the cloud that users have been exerting (Khajeh- Hosseini, A, Ian Sommerville, Bogaerts, J and Teregowda, P., 2011). Last but not least, the lack of interoperability standards comes into any cloud computing. What makes this issue more difficult to create a suitable security function is that there is no firm communication and data export concept between and within CSP (Pearson, S. and Benameur, A., 2010). Thus, an acceptation of general standards is considered to guarantee inter-operability among providers (Harauz, J, Kauifman, M and Potter, B., 2009) 2. Risks from cloud customer perspective 2.1 Physical security When the CSP store data redundantly in several physical locations, the data location is not disclosed to their customers. As a consequence, the users find it difficult to figure out if appropriate security solutions are the same as their secure data (21). The customers cannot handle the downtime of the cloud computing when it runs ineffectively because of CSP machines. This can cause troubles to the users and immensely discourages them to continue with the cloud (34) 2.2 Data security, privacy & control risks - User Access Control: User access control is an important part of any information system which ensures only authorized users have the right to access the applications and data storage (Sabahi, 2011). The customers have a full responsibilities for all software security controls, including application access control, IAM, software patching, and virus protection (24). Depending on the types of the cloud service, users take different responsibilities. In SaaS, the customers assures that only intended users gain the right to access by controlling passwords and internal resemblance. With regard to PaaS model, customers are responsible for managing access to 140
  11. particular application hosted by the provider. Towards IaaS model, the users must monitor all aspects of access control, even resources namely host platform and network, etc. Moreover, they must guarantee their virtual machines and stored data as well (Sabahi, 2011). - Data privacy and security: One of the most concerned problems for the end-users is how to manage privacy and protection of their data from the CSP so as to assure that storage is not compromised. But in some cases, the customers have a duty in monitoring their confidential and safe data even while it resides on provider premises (15). When the cloud service losses encryption key or privileged codes, it leads a threating issue to cloud users (36). The consumers will deal with the damage of data loss and accidental leakage of data outside the cloud because of a loss of cryptographic management information (24). Unfortunately, the CSA (Cloud Security Alliance) predicts that preventing data loss does not submerge entirely. Even if a user encrypts data before moving it in the cloud or lost the encryption keys, loss data will occur (30). - Data Segregation and Secure Data Deletion: In terms of data segregation, the responsibility of the customers is to find out the technical methods to isolate data, additionally to the guarantee that the encryption schemes are productive enough to provide security and are deployed (29). However, deploying encryption should not be suggested as sole measure since in specific situations, the users do not want to encrypt data in which it may ruin the data (23). Regarding data deletion, it occurs with error free and timely data deletion. This results in adding copies of data in various locations or the disk including data from other clients is destroyed (19). This data is destroyed completely as it is expired to utilize. With physical characteristics of storage medium, the deleted data somehow exists or is stored which poses another risk of sensitive data disclosure (11). - Data Availability, Loss of Control and Backup: When user data is uploaded to the cloud, the data on the cloud are not in their complete possession anymore. Thus, personal data and information from clients can possibly be lost or hacked without the chance of getting the original data back (31). Though it must be fixed by the service providers, the users along with the CSP need to agree with particular specification regarding system availability (Zissis & Lekkas, 2012). A larger part of data availability is the loss of control which refers to the user not being able to access to the physical hardware being used. The most basic step to avoid this problem is evaluating the stored data in the cloud whether it is risky or not by previous violation agreements with cloud owners (Zissis & Lekkas, 2012) (Al-anzi, Salman, Jacob & Soni, 141
  12. 2014). If sensitive data is seen as violation of data privacy owing to loss of control, customer had better consider to place their storage and processing. Besides, it is essential to pick up a trustworthy cloud service provider and carefully evaluate cloud service security solutions (Xiao & Xiao, 2013). Another loss of control for the user is the fact that the service provider could gain access to user’s stored data. The solutions are many but no single solution can fully prevent malicious administrators from reading and manipulating the data. The first solution is to never give the provider further privilege than they basically possess in order to prevent an individual from controlling all data and functions (Varadharajan & Tupakula, 2014). The second solution is encrypting all data in the cloud though it is not feasible to encrypt a huge quantity of data from a performance standpoint. The alternative is to conduct some computing tasks without decryption, granting the cloud owner much more control of data (Tari, 2014). Eventually, assuring data counteracting data loss is by carrying out backups. For the users, remaining a local backup (hardware storage) of everything in the cloud is the most effective measure. Nevertheless, there is an obstacle to consider that it is relatively not saving, go against the purpose of the cloud that store user’s data and information (Khalil, Khreishah, Bouktif, & Ahmad, 2013). 2.3 Technical risks Aside from private, secure and physical risks, there are still threats relating to technical problem naturally (Grobauer, Walloschek, & Stocker, 2011). According to K. Popovic and Z.Hocenski, the portability emerges as the user want to change from one provider to another because the storage service from this provider might not compatible with that provider’s service system (32). A drastically risk is a denial of service attack using account lockouts. The moment that an authorized user locks account due to a failure of login attempts the hackers will deny service to a large number of users if they get their account names by login with username and arbitrary password to lock account (Grobauer, Walloschek, & Stocker, 2011). Regarding the above issue a weak password reset mechanisms are described as a technical risk. One benefit is that they can regain access by resetting the password from locking out the account. But this brings a trouble of loss control, except this must be conducted in safe manners otherwise the attackers could gain control of account from the user (Grobauer, Walloschek, & Stocker, 2011). While potential solution is launched such as more secure password reset mechanism, a clear policy that authorized users legitimately take their account back in case of a lockout. In detail, this specifies that the users need to identify themselves before resetting password and who can manage the password reset function. Only a trustworthy entity at organization using cloud have the privilege of identifying users requesting their password reset and approving 142
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