When they receive your credit card details, an online review of your credit card will be carried out with your receiving bankers. This process ensures that the number you entered actually corresponds to a real credit card number and is not a fake card. The CyberSource system also checks various "hot card lists" to ensure that no credit cards are being used fraudulently. This online check of your data takes place via a secure line to the bank. Credit card details are never sent over the Internet as part of the validation process. They also perform random security checks on cards to prevent fraud.