The greatest concern for an IS auditor reviewing an organization's disaster recovery plan (DRP) is that the DRP has not been updated since an IT infrastructure upgrade. This could render the DRP obsolete or ineffective, as it may not reflect the current configuration, dependencies or recovery requirements of the IT systems. The IS auditor should ensure that the DRP is reviewed and updated regularly to align with any changes in the IT environment. The DRP has not been formally approved by senior management is a concern for an IS auditor reviewing an organization's DRP, but it is not as critical as ensuring that the DRP is up to date and valid. The DRP has not been distributed to end users or the DRP contains recovery procedures for critical servers only are issues that relate to the communication or scope of the DRP, but not to its validity or effectiveness. References: ISACA, CISA Review Manual, 27th Edition, 2018, page 389

The IS auditor's best course of action when preparing the final report is to include the position supported by senior management in the final engagement report. The IS auditor should communicate the audit findings and recommendations to senior management and obtain their feedback and approval before issuing the final report. If there is a disagreement between the auditee and the IS auditor regarding a recommendation for corrective action, the IS auditor should present both sides of the argument and the supporting evidence, and seek senior management's opinion and decision. The IS auditor should respect and follow senior management' s position, and include it in the final engagement report, along with the auditee's comments if applicable. The other options are not the best course of action, because they either do not resolve the disagreement, do not reflect senior management's authority, or do not report the audit results accurately and completely.
References: CISA Review Manual (Digital Version)1, Chapter 2, Section 2.2.5

A demilitarized zone (DMZ) is a network segment that is separated from the internal network and the external network, such as the internet, by firewalls or other security devices. A DMZ provides an extra layer of security for the organization's internal network by isolating the servers and services that need to be accessible to external users, such as a file server, from the rest of the network. A DMZ also prevents external users from accessing the internal network directly, as they have to go through two firewalls to reach it. Therefore, setting up a DMZ is an IS auditor's best recommendation to protect an organization from attacks when its file server needs to be accessible to external users12.
The other possible options are:
* Enforce a secure tunnel connection: This means that the organization requires external users to establish a secure and encrypted connection, such as a virtual private network (VPN), to access its file server.
This can provide some level of security and privacy for the data transmission, but it does not protect the file server or the internal network from attacks if the connection is compromised or if the external users are malicious. Therefore, enforcing a secure tunnel connection is not an IS auditor's best recommendation to protect an organization from attacks when its file server needs to be accessible to external users3.
* Enhance internal firewalls: This means that the organization improves the security and performance of its internal firewalls, which are devices that filter and control the network traffic between different segments of the network. This can provide some level of protection for the internal network from unauthorized or malicious access, but it does not protect the file server or the external network from attacks if the file server is exposed to the internet or if the external network is compromised. Therefore, enhancing internal firewalls is not an IS auditor's best recommendation to protect an organization from attacks when its file server needs to be accessible to external users4.
* Implement a secure protocol: This means that the organization uses a secure and standardized protocol, such as Secure File Transfer Protocol (SFTP) or Secure Shell (SSH), to transfer files between its file server and external users. This can provide some level of security and integrity for the data transmission, but it does not protect the file server or the internal network from attacks if the protocol is exploited or if the external users are malicious. Therefore, implementing a secure protocol is not an IS auditor's best recommendation to protect an organization from attacks when its file server needs to be accessible to external users5. References: 1: What Is a DMZ Network and Why Would You Use It? | Fortinet 2: Demilitarised zone (DMZ) | Cyber.gov.au 3: What Is VPN Tunneling? | Fortinet 4: Firewall
- Wikipedia 5: Secure Shell - Wikipedia

The most important consideration for an IS auditor when scheduling follow-up activities for agreed-upon management responses to remediate audit observations is the risk rating of original findings. The risk rating of original findings is an assessment of the potential impact or likelihood of an audit issue or observation on the organization's objectives, operations, or reputation. The risk rating of original findings can help determine the priority and urgency of follow-up activities for agreed-upon management responses to remediate audit observations by ensuring that high-risk issues are addressed first and more frequently than low-risk issues.
The other options are not as important as the risk rating of original findings in scheduling follow-up activities for agreed-upon management responses to remediate audit observations, as they do not reflect the significance or severity of audit issues or observations. Business interruption due to remediation is a possible consequence of implementing corrective actions to address audit issues or observations, but it does not indicate the priority or urgency of follow-up activities. IT budgeting constraints is a possible factor that may affect the availability or feasibility of resources for implementing corrective actions to address audit issues or observations, but it does not indicate the priority or urgency of follow-up activities. Availability of responsible IT personnel is a possible factor that may affect the accountability or responsiveness of staff for implementing corrective actions to address audit issues or observations, but it does not indicate the priority or urgency of follow-up activities. References: CISA Review Manual (Digital Version), Chapter 2, Section 2.4

Segregation of duties is a key internal control that aims to prevent fraud and errors by ensuring that no single individual has the authority to execute two or more conflicting sensitive transactions or functions. In the accounts payable vendor payment cycle, segregation of duties involves separating the tasks of vendor setup, procurement, invoice approval, and payment processing1. This way, an employee cannot create a fictitious vendor and issue a payment to themselves or their accomplices without being detected by another person. Therefore, the best way to prevent fraudulent payments is to implement segregation of duties between the vendor setup and payment processing. References: 1: Segregation of Duties in the Accounts Payable Vendor Payment Cycle for SMBs - Now With a Podcast! - Debra R Richardson : What is Separation of duties
- University of California, Berkeley