The major advantage of automating internal controls is to efficiently test large volumes of data, because automated controls can perform repetitive tasks faster, more accurately, and more consistently than manual controls. Automated controls can also provide audit trails and exception reports that facilitate the monitoring and evaluation of the control effectiveness12. Reviewing large value transactions, identifying transactions with no segregation of duties, and performing analytical reviews are possible benefits of automating internal controls, but not the major advantage. References: 1: CISA Review Manual (Digital Version), Chapter 5, Section 5.2.2 2: CISA Online Review Course, Module 5, Lesson 2

The best audit evidence that a firewall is configured in compliance with the organization's security policy is to review the rule base. The rule base is a set of rules that defines the criteria for allowing or denying network traffic through the firewall. By reviewing the rule base, the auditor can verify if the firewall configuration matches the security policy requirements and objectives. Analyzing how the configuration changes are performed, analyzing log files, and performing penetration testing are useful audit techniques, but they do not provide direct evidence of the firewall configuration compliance. References: CISA Review Manual (Digital Version)1, page 383.

The best recommendation to prevent unauthorized access to a highly sensitive data center by piggybacking or tailgating is to use an airlock entrance. An airlock entrance is a type of access control system that consists of two doors that are interlocked, so that only one door can be opened at a time. This prevents an unauthorized person from following an authorized person into the data center without being detected. An airlock entrance can also be integrated with other security measures, such as biometrics, card readers, or PIN pads, to verify the identity and authorization of each person entering the data center.
Biometrics (option A) is a method of verifying the identity of a person based on their physical or behavioral characteristics, such as fingerprints, iris scans, or voice recognition. Biometrics can provide a high level of security, but they are not sufficient to prevent piggybacking or tailgating, as an unauthorized person can still follow an authorized person who has been authenticated by the biometric system.
Procedures for escorting visitors (option B) is a policy that requires all visitors to the data center to be accompanied by an authorized employee at all times. This can help prevent unauthorized access by visitors, but it does not address the risk of piggybacking or tailgating by other employees or contractors who may have legitimate access to the building but not to the data center.
Intruder alarms (option D) are devices that detect and alert when an unauthorized person enters a restricted area. Intruder alarms can provide a deterrent and a response mechanism for unauthorized access, but they are not effective in preventing piggybacking or tailgating, as they rely on the detection of the intruder after they have already entered the data center.
References: 1: CISA Certification | Certified Information Systems Auditor | ISACA 2: CISA Certified Information Systems Auditor Study Guide, 4th Edition 3: CISA - Certified Information Systems Auditor Study Guide [Book]

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

The recovery time objective (RTO) is the most important consideration when making a decision to invest in a hot site due to service criticality. The RTO is the maximum acceptable time that an IT service or process can be unavailable or disrupted before it causes significant damage to the business operations and objectives. A hot site is a fully equipped and operational backup facility that can be activated immediately in the event of a disaster or disruption. A hot site can help an organization achieve a very low RTO, as it can resume the service with minimal or no downtime. The maximum tolerable downtime (MTD) is the maximum acceptable time that an IT service or process can be unavailable or disrupted before it causes intolerable damage to the business operations and objectives. The MTD is usually longer than the RTO, as it represents the worst-case scenario. The recovery point objective (RPO) is the maximum acceptable amount of data loss that an IT service or process can tolerate in the event of a disaster or disruption. The RPO is measured in terms of time, such as hours or minutes, and indicates how frequently the data should be backed up or replicated. The mean time to repair (MTTR) is the average time that it takes to restore an IT service or process after a failure or disruption. The MTTR is a measure of the efficiency and effectiveness of the recovery process, but it does not reflect the service criticality or the business impact. References: IS Audit and Assurance Tools and Techniques, CISA Certification | Certified Information Systems Auditor | ISACA