A data loss prevention (DLP) control is a technology that tries to detect and stop sensitive data breaches, or data leakage incidents, in an organization. A DLP control is used to prevent sensitive data, such as credit card numbers, from being disclosed to an unauthorized person, whether it is deliberate or accidental1. The best way to help ensure the effectiveness of a DLP control that has been implemented to prevent the loss of credit card data is to test the transmission of credit card numbers. This is a technique to verify that the DLP control can successfully identify and block the credit card data when it is sent or received through various channels, such as email, messaging, or file transfers. Testing the transmission of credit card numbers can help to evaluate the accuracy and reliability of the DLP control, as well as to identify and correct any false positives or false negatives. The other options are not the best ways to help ensure the effectiveness of a DLP control that has been implemented to prevent the loss of credit card data, although they may be helpful and complementary. Reviewing logs forunauthorized data transfers is a technique to monitor and analyze the DLP control activities and incidents, such as who, what, when, where, and how the data was transferred. However, reviewing logs is a reactive and passive approach, while testing the transmission is a proactive and active approach. Configuring the DLP control to block credit card numbers is a technique to set up the DLP control rules and policies, such as defining the data patterns, the detection methods, and the response actions. However, configuring the DLP control is a prerequisite and a preparation step, while testing the transmission is a validation and a verification step. Testing the DLP rule change control process is a technique to ensure that the DLP control rules and policies are updated and maintained in a controlled and coordinated manner, such as obtaining approval, documenting the changes, testing the changes, and communicating the changes. However, testing the DLP rule change control process is a quality and governance step, while testing the transmission is a performance and functionality step. References = What is Data Loss Prevention (DLP)? | Digital Guardian1; CRISC Review Manual, pages 164-1652; CRISC Review Questions, Answers & Explanations Manual, page 833