Comprehensive and Detailed Step-by-Step Explanation:
To efficiently detectduplicate payments,data analyticsand automated checks are required due to thehigh volume of transactions.
* Option A (Correct):Computer-Assisted Audit Techniques (CAATs)allow auditors toautomatically scan large datasetsfor duplicate payments based oninvoice numbers, vendor names, and payment amounts.
* Option B (Incorrect):Stratified samplinggroups data into categories, which helps in analysis but does not directly detect duplicates.
* Option C (Incorrect):Statistical samplingis useful forextrapolating results, but it doesnot systematically findduplicate transactions.
* Option D (Incorrect):Process walk-throughsreview procedures but donot analyze transactions at scale.
Reference:ISACA CISA Review Manual -Domain 2: Governance and Management of IT- Covers CAATs, data analytics, and fraud detection techniques.

IT disaster recovery time objectives (RTOs) are the maximum acceptable time that an IT system can be unavailable after a disaster before it causes unacceptable consequences for the business. IT RTOs should be based on the business-defined criticality of the systems, which reflects how important they are for supporting the business processes and functions. The maximum tolerable loss of data, the nature of the outage, and the maximum tolerable downtime (MTD) are also factors that affect the IT RTOs, but they are not the primary basis for determining them.

An audit report of the controls by the service provider's external auditor provides the best evidence that a third-party service provider's information security controls are effective. An external auditor is an independent and objective party that can assess the design and operating effectiveness of the service provider' s information security controls based on established standards and criteria. An external auditor can also provide an opinion on the adequacy and compliance of the service provider's information security controls, as well as recommendations for improvement.
Documentation of the service provider's security configuration controls is a source of evidence that a third- party service provider's information security controls are effective, but it is not the best evidence.
Documentation of the security configuration controls can show the settings and parameters of the service provider's information systems and networks, but it may not reflect the actual implementation and operation of the controls. Documentation of the security configuration controls may also be outdated, incomplete, or inaccurate.
An interview with the service provider's information security officer is a source of evidence that a third-party service provider's information security controls are effective, but it is not the best evidence. An interview with the information security officer can provide insights into the service provider's information security strategy, policies, and procedures, but it may not verify the actual performance and compliance of the information security controls. An interview with the information security officer may also be biased, subjective, or misleading.
A review of the service provider's policies and procedures is a source of evidence that a third-party service provider's information security controls are effective, but it is not the best evidence. A review of the policies and procedures can show the service provider's information security objectives, requirements, and guidelines, but it may not demonstrate the actual execution and enforcement of the information security controls. A review of the policies and procedures may also be insufficient, inconsistent, or outdated.
References:
* ISACA, CISA Review Manual, 27th Edition, 2019, p. 284
* ISACA, CISA Review Questions, Answers & Explanations Database - 12 Month Subscription

A digital signature is the most appropriate control to ensure integrity of online orders because it provides a way to verify the authenticity and integrity of the data sent by the sender. A digital signature is created by applying a cryptographic algorithm to the data and attaching the result to the data. The receiver can then use the sender's public key to verify that the data has not been altered or tampered with during transmission. A digital signature also provides non-repudiation, which means that the sender cannot deny sending the data.
Data Encryption Standard (DES) is a symmetric encryption algorithm that can provide confidentiality of online orders, but not integrity. DES uses the same key to encrypt and decrypt the data, which means that anyone who has the key can modify the data without detection.
Public key encryption is an asymmetric encryption algorithm that can also provide confidentiality of online orders, but not integrity. Public key encryption uses a pair of keys: a public key and a private key. The sender encrypts the data with the receiver's public key, and the receiver decrypts it with their own private key.
However, public key encryption does not prevent anyone from modifying the encrypted data.
Multi-factor authentication is a control that can provide authentication and authorization of online orders, but not integrity. Multi-factor authentication requires the user to provide two or more pieces of evidence to prove their identity, such as a password, a token, or a biometric factor. Multi-factor authentication can prevent unauthorized access to online orders, but it does not protect the data from being modified after being sent.
References:
* ISACA, CISA Review Manual, 27th Edition, 2019, p. 281 1
* ISACA, CISA Review Questions, Answers & Explanations Database - 12 Month Subscription 2

Comprehensive and Detailed Step-by-Step Explanation:
Audit findings should be communicated as early as possible to avoid misunderstandings, provide an opportunity for corrective action, and ensure transparency.
* Option A (Incorrect):The planning phase involves defining audit scope, objectives, and methodology, but findings are not yet available to discuss with management.
* Option B (Incorrect):The reporting phase formalizes audit results, but discussing issuesonlyat this stage may lead to delays in corrective action.
* Option C (Incorrect):The follow-up phase ensures that management has implemented corrective actions, but this occursafterthe initial discussion of findings.
* Option D (Correct):The fieldwork phase is when auditors activelygather evidence, analyze data, and identify issues. Discussing observationsduringthis phase allows for immediate clarification, validation, and resolution of misunderstandings before the final report.
Reference:ISACA CISA Review Manual -Domain 1: Information Systems Auditing Process- Discusses audit engagement, reporting, and communication best practices.