The best way to prevent accepting bad data from a third-party service provider is to implement business rules to reject invalid data. Business rules are logical statements that define the data quality requirements and standards for the organization. By implementing business rules, the organization can ensure that only data that meets the predefined criteria is accepted into the enterprise data warehouse. Obtaining error codes indicating failed data feeds, purchasing data cleansing tools from a reputable vendor, and appointing data quality champions across the organization are useful measures to improve data quality, but they do not prevent accepting bad data in the first place. References: ISACA Journal Article: Data Quality Management

The first course of action that the auditor should recommend after finding that several employees are spending an excessive amount of time using social media sites for personal reasons is to implement policies addressing acceptable usage of social media during working hours. Policies can help define the scope, purpose, rules, and expectations of using social media in the workplace, both for personal and professional reasons. Policies can also specify the consequences of violating the policies, such as disciplinary actions or termination. Policies can help deter employees from misusing social media at work, which could affect their productivity, performance, or security. Policies can also help protect the organization from legal liabilities or reputational damages that could arise from inappropriate or unlawful employee behavior on social media.

Antivirus software has been implemented on the guest operating system only is the observation that an IS auditor would consider the greatest risk when conducting an audit of a virtual server farm for potential software vulnerabilities. A virtual server farm is a collection of servers that run multiple virtual machines (VMs) on a single physical host using a software layer called a hypervisor. A guest operating system is the operating system installed on each VM. Antivirus software is a software program that detects and removes malicious software from a computer system. If antivirus software has been implemented on the guest operating system only, it means that the hypervisor and the host operating system are not protected from malware attacks, which could compromise the security and availability of all VMs running on the same host.
Therefore, antivirus software should be implemented on both the guest and host operating systems as well as on the hypervisor. References: CISA Review Manual, 27th Edition, page 378