A backdoor refers to a generally undocumented means of getting into a system, mostly for programming and maintenance/troubleshooting needs. Most real world programs have backdoors. Creating backdoors is how a hacker can insure his ability to return to the hacked system at will.

The answer A is correct because the greatest concern for an IS auditor when a data owner assigns an incorrect classification level to data is that controls to adequately safeguard the data may not be applied. Data classification is the process of categorizing data assets based on their information sensitivity and business impact. Data classification helps organizations to identify, protect, and manage their data according to their value and risk. Data owners are the individuals or entities who have the authority and responsibility to define, classify, and control the access and use of their data.
Data classification typically involves assigning labels or tags to data assets, such as public, internal, confidential, or restricted. These labels indicate the level of protection and handling required for the data.
Based on the data classification, organizations can implement appropriate controls to safeguard the data, such as encryption, access control lists, audit logs, backup policies, etc. These controls help to prevent unauthorized access, disclosure, modification, or loss of data, and to ensure compliance with relevant laws and regulations.
If a data owner assigns an incorrect classification level to data, it can result in either underprotection or overprotection of the data. Underprotection means that the data is classified at a lower level than it should be, which exposes it to higher risks of compromise or breach. For example, if a data owner classifies personal health information (PHI) as public instead of confidential, it may allow anyone to access or share the data without proper authorization or consent. This can violate the privacy rights of the data subjects and the compliance requirements of regulations such as HIPAA (Health Insurance Portability and Accountability Act). Overprotection means that the data is classified at a higher level than it should be, which limits its availability or usability. For example, if a data owner classifies marketing materials as restricted instead of public, it may prevent potential customers or partners from accessing or viewing the data. This can reduce the business value and opportunities of the data.
Therefore, an IS auditor should be concerned about the accuracy and consistency of data classification by data owners, as it affects the security and efficiency of data management. An IS auditor should review the policies and procedures for data classification, verify that the data owners have adequate knowledge and skills to classify their data, and test that the data classification labels match with the actual sensitivity and impact of the data.
References:
* Data Classification: What It Is and How to Implement It
* What Is Data Classification? - Definition, Levels & Examples ...
* Data Classification: A Guide for Data Security Leaders

Section: Protection of Information Assets
Explanation
Explanation:
Collusion is an active attack that can be sustained and is difficult to identify since even well-thought-out
application controls may be circumvented. The other choices do not impact well-designed application
controls.

The best recommendation for an organization that is unable to add new servers on demand in a cost-efficient manner is to build a virtual environment. A virtual environment is a technology that allows multiple virtual machines to run on a single physical server, sharing its resources and capabilities. A virtual environment can help the organization add new servers on demand in a cost-efficient manner by reducing the need for hardware acquisition, maintenance, and power consumption. The other options are not as effective as building a virtual environment, as they do not address the root cause of the problem or provide the same benefits.
Increasing the capacity of existing systems is a short-term solution that can help improve the performance and availability of the current servers, but it does not enable the organization to add new servers on demand in a cost-efficient manner. Upgrading hardware to newer technology is a costly solution that can help enhance the functionality and reliability of the servers, but it does not enable the organization to add new servers on demand in a cost-efficient manner. Hiring temporary contract workers for the IT function is an irrelevant solution that can help supplement the IT staff's skills and knowledge, but it does not enable the organization to add new servers on demand in a cost-efficient manner. References: CISA Review Manual (Digital Version), Chapter 3, Section 3.3.1