A CVV number is a three or four digit security code most commonly seen on a credit card. The primary function of the CVV number is to verify that the user has physical access to the corresponding card, hence providing an added layer of security against credit card fraud.

How do they work?

For most cards, the last digit of the number is a check-sum, in which all cards in a given series will have the same last digit.

For example:

The first six digits represent information about the card issuer and card type. The next three digits indicate the card’s authentication code (a password used to authorize transactions). The last digit is a check code.

The CVV number is not encoded on the magnetic strip of most cards, so it serves as a second layer of verification when using your card to make internet purchases. In some countries, including the USA and Canada, merchants are required by law to ask for the CVV number in order to process payments via credit or debit cards. In other cases, the merchant may be required to ask for your billing address confirmation.

What should I do if I receive a CVV Number Notice?

If you find that you are receiving this message with greater frequency than usual, it can easily be resolved by updating your credit card expiration date or issuing bank’s security procedures. If you are receiving the message unexpectedly, it may be because your credit card company has flagged you as a risk of fraud. You should contact your credit card company immediately to inform them that you are not responsible for these charges.

Why are they necessary?

CVV numbers help protect against potential fraud by verifying that people making purchases have access to the physical card. When you make an online purchase, the issuing bank requests a three or four digit CVV number from your credit card company before allowing the transaction to go through. If the number does not match what is on file with your bank, this indicates that someone may be trying to use your card fraudulently. The issuer will then request that the credit card company cancel your card number.

Can I remove them?

Users of paypal can contact paypal and have their accounts flagged so that no more CVV notices are displayed. It is important to remember not to enter your pin when entering your CVV information. However, many users find this flag inconvenient or unfair for purchases that require the use of a credit card.

In this case, it is possible to prevent displaying the CVV number on all sites except those where you are making a purchase. In your browser’s address bar, enter “about:config” and press Enter/Return. The warning message displayed by Firefox regarding modifying preferences should be taken very seriously. Once you have read it, click “I’ll be careful, I promise!” (you may need to scroll down in order to see this).

You will be presented with a long list of preferences that are grouped into different categories. You can modify these settings by changing their value either directly or by searching for them in the search bar in the upper right part of your screen.