# Secure Cloud Infrastructure: A Survey on Issues, Current Solutions, and Open Challenges
## 6 Open Challenges  
While cloud computing has been widely embraced by businesses and industries, cloud computing research is still immature. Many of the current gaps regarding the cloud infrastructure have not been completely addressed, while new challenges continue to arise. The following subsections summarize the most important open challenges that need to be studied further. Securing Hypervisor  
An insecure hypervisor is a serious challenge that threatens cloud computing. It can damage the entire system [21]. Traditional detection/prevention solutions are not efficient enough with the dynamic nature of the cloud. The cloud needs context-aware solutions to differentiate between normal and abnormal behaviors. Additionally, any proposed solution should take immediate action to avoid damaging the cloud infrastructure or disrupting the normal operations. The popularity and rapid growth of cloud-based information storage services have generated controversy about the integrity of cloud-based data, which can be lost or destroyed because of unavoidable hardware-software failures and/or human-related errors. The third-party auditor should provide expert integrity verification services. During public auditing of cloud information, the content of the private information of the individual client should not be revealed to any public verifier. As a result, a new major issue regarding privacy, and more specifically the leakage of data privacy to third-party auditors, has been being introduced. It remains a difficult research challenge to establish solutions that ensure the integrity of cloud storage security and privacy. Under security breaches, the system must be able to continue its normal operations. Availability also refers to the data, software and hardware available to approved users based on demand. System availability incorporates the capacity of the framework to carry out operations at all times. Data availability, protection, and data security stand out amongst the most perplexing challenges of the cloud environment up to now. Data remanence is the presence of residual data even after deletion, reformatting, or reallocation of it to another person. This is a major threat to the confidentiality of deleted files (passwords, encryption keys, government data, financial or health data, etc.). Data remanence may be discovered by computer forensics and other various techniques. In addition, it is possible to find and recover files that might have been removed from a computer [103]. Cloud providers have not fully addressed data remanence, and this issue is even ignored by some cloud providers, even though it is one of the most critical issues. At the network level, the proposed security mechanisms were presented to be defensive in IaaS, such as a dynamic DNS firewall that protects against attack, as mentioned in [83]. However, there are still a lot of attacks that cannot be resolved with a traditional firewall. The DNS attack is an increased risk in cloud computing due to the several attacks that are identified as a consequence of it. In addition, there are few research efforts aboutreusing IP addresses, which leads to serious data and system breaches from a customer security perspective. Due to the obvious cloud-specific characteristics, conventional access control and identity management techniques are not suitable for promoting IaaS security. New technologies such as blockchain and computational intelligence should be used in this regard to provide sufficient security in this new computing environment. Authentication  
Most authentication solutions are time-consuming and complex. Existing studies tested their techniques via simulation with a small amount of data, less complex resources and a smaller number of users. However, the cloud in reality has a huge number of users and other complex features. Therefore, more effort should be given to developing techniques that take into consideration all of these constraints.