# 3D-Secure **3-D Secure** – a protocol used as an extra layer of security for online credit and debit cards for second-factor authentication of a user. **Purpose** – authentication of a card holder and protection against unauthorized use of the card **How it works**: the cardholder enters the card details, and then the issuer's website opens where the holder is asked to enter a password or a secret code. In most cases, a code is sent as a SMS message. If the code is entered correctly, the payment will be proceeded. Otherwise, the payment will be declined. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://docs.tarlanpayments.kz/eng/acquiring/welcom/3d-secure.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.