Hashing is a technique that transforms data into a fixed-length value, called a hash or a digest, that uniquely represents the original data. Hashing can be used to validate the integrity of data communicated between production databases and a big data analytics system by comparing the hash values of the data before and after the communication. If the hash values match, the data has not been altered; if they differ, the data has been tampered with or corrupted. Hashing is a better security control than encrypting, running and comparing the count function, or hosting a digital certificate for this purpose because:
Encrypting in-scope data sets can protect the confidentiality of the data, but not necessarily the integrity.
Encryption algorithms can be broken or bypassed by malicious actors, or encryption keys can be compromised or lost. Moreover, encryption adds overhead to the communication process and may affect the performance of the big data analytics system.
Running and comparing the count function within the in-scope data sets can only verify the number of records or elements in the data sets, but not the content or quality of the data. The count function cannot detect any changes or errors in the data values, such as missing, duplicated, corrupted, or manipulated data.
Hosting a digital certificate for in-scope data sets can provide authentication and non-repudiation for the data sources, but not integrity for the data itself. A digital certificate is a document that contains information about the identity and public key of an entity, such as a person, organization, or device. A digital certificate does not contain or verify the actual data that is communicated between production databases and a big data analytics system.
References:
Ensuring Data Integrity with Hash Codes
Database Security: An Essential Guide
Control methods of Database Security

The best recommendation is to place an intrusion detection system (IDS) between the firewall and the Internet. An IDS is a device or software that monitors network traffic for malicious activity and alerts the network administrator or takes preventive action. By placing an IDS between the firewall and the Internet, the IS auditor can enhance the security of the network perimeter and detect any attack attempts that the firewall was unable to recognize.
The other options are not as effective as placing an IDS between the firewall and the Internet:
* Placing an IDS between the firewall and the organization's web server would not protect the web server from external attacks that bypass the firewall. The web server should be placed in a demilitarized zone (DMZ), which is a separate network segment that isolates public-facing servers from the internal network.
* Placing an IDS between the firewall and the demilitarized zone (DMZ) would not protect the DMZ from external attacks that bypass the firewall. The DMZ should be protected by two firewalls, one facing the Internet and one facing the internal network, with an IDS monitoring both sides of each firewall.
* Placing an IDS between the firewall and the organization's network would not protect the organization' s network from external attacks that bypass the firewall. The organization's network should be protected by a firewall that blocks unauthorized traffic from entering or leaving the network, with an IDS monitoring both sides of the firewall.

The best way to help ensure new IT implementations align with enterprise architecture (EA) principles and requirements is to conduct EA reviews as part of the change advisory board (CAB). A CAB is a committee that evaluates and authorizes changes to IT services, such as new IT implementations. By conducting EA reviews as part of the CAB process, the organization can ensure that the proposed changes are consistent with the EA vision, goals, standards, and guidelines. This can help avoid potential conflicts, risks, or inefficiencies that may arise from misaligned IT implementations. Additionally, EA reviews can help identify opportunities for improvement, optimization, or innovation in the IT services.
The other options are not the best ways to help ensure new IT implementations align with EA principles and requirements. Documenting the security view as part of the EA is important, but it does not guarantee that new IT implementations will follow the security requirements or best practices. Considering stakeholder concerns when defining the EA is also essential, but it does not ensure that new IT implementations will meet the stakeholder expectations or needs. Performing mandatory post-implementation reviews of IT implementations is a good practice, but it does not prevent potential issues or problems that may arise from misaligned IT implementations.
References:
* 5: Change Advisory Board Best Practices: 15+ Industry Leaders Weigh In
* 6: What Does the Change Advisory Board (CAB) Do?
* 7: How do I set up an effective change advisory board? - ServiceNow
* 8: ITIL Change Management - The Role of the Change Advisory Board

The use of control totals satisfies the control objective of processing integrity. Processing integrity refers to the accuracy, completeness, timeliness, and validity of data processing. Control totals are a method of verifying the correctness of data processing by comparing the total value or count of a batch of transactions before and after processing. For example, if a batch of 100 invoices is entered into an accounting system, the total amount and number of invoices should match before and after processing. If there is a discrepancy, it indicates an error in data entry, transmission, or processing. Control totals help to ensure that no transactions are lost, duplicated, or altered during processing.
References:
* Control Objectives & Activities: Examples, Appropriateness
* Levels and Types of Control | Principles ofManagement
* CISA Review Manual 27th Edition, page 337