Which of the following is considered "Sensitive Authentication Data"?

The term "Sensitive Authentication Data" refers to information that is critical to the security of payment card transactions and should be protected under the PCI DSS standards. The card verification value, often referred to as CVV or CVV2, is a three- or four-digit number printed on the back of credit cards. It serves as an additional security feature and is used to validate that the card is in the possession of the cardholder during remote transactions, such as online purchases.

The CVV is sensitive because it is designed to prevent fraud in scenarios where the physical card is not present. Revealing this data can lead to unauthorized transactions, making it crucial to store and handle it appropriately.

In contrast, while a PIN is also sensitive, it is explicitly classified under different guidelines and may not be included in the same category as data primarily associated with card-not-present transactions. The account number, although important and sensitive, is not classified as authentication data but rather as cardholder data. Lastly, a transaction number is not sensitive authentication data, as it typically serves to identify a specific transaction rather than validate the authenticity of the cardholder during the transaction.

Thus, among the options provided, the card verification value stands out as the correct choice for Sensitive Authentication Data.