This is a way to verify who you are, and to identify the account you are referring to.
The last 4 digits are very easy to learn for a person seeking to steal an identity. It can be obtained from your trash, someone cleaning your house, or just passing by your desk at work.
The first 4-6 are the Bank Identification Number. Most banks have many different BIN’s, so they’re not easy to guess.
You are not providing
- The middle (6) number on your card is literally one in a million. So without that, nobody is going to be able to obtain your card number.
- The Card Verification Value (CVV) number, on the back of your card, which must be provided on an internet transaction.
By providing the first 6 last 4, the are able to establish your identity in a secure manner, with little chance of you not being who you say you are.
If you have found this site because of an unknown charge on your credit card, you are going to cancel your card anyway, so it is OK to give them the partial number.