Methods and apparatus for preventing fraud in payment processing transactions

1. A method comprising:

receiving, by a payment system computer, an authorization request for a purchase transaction;

determining, by the payment system computer, that the authorization request arose from proximity-reading a proximity payment device;

determining that a first account number in the authorization request is qualified for mapping;

mapping the first account number included in the authorization request into a second account number associated with the first account;

transmitting the authorization request to an issuer financial institution with the second account number substituted for the first account number in the authorization request;

receiving, by the payment system computer, an authorization response from the issuer financial institution, said authorization response including said second account number;

mapping the second account number to the first account number; and

transmitting the authorization response to an acquirer financial institution with the first account number substituted for the second account number in the authorization response.

2. The method of claim 1 , further comprising:

including the second account number as auxiliary data in the authorization response transmitted to the acquirer financial institution.

3. The method of claim 1 , wherein the second account number is a primary account number that identifies a payment card account.

4. The method of claim 3 , wherein:

said proximity payment device is associated with said payment card account; and

said first account number is assigned to said proximity payment device.

5. The method of claim 1 , further comprising:

including the first account number as auxiliary data in the authorization request transmitted to the issuer financial institution.

6. A system comprising a storage device and a processor, wherein the storage device storing instructions configured to cause the processor to:

receive an authorization request for a purchase transaction;

determine that the authorization request arose from proximity-reading a proximity payment device;

determine that a first account number in the authorization request is qualified for mapping;

map the first account number included in the authorization request into a second account number associated with the first account;

transmit the authorization request to an issuer financial institution with the second account number substituted for the first account number in the authorization request;

receive an authorization response from the issuer financial institution, said authorization response including said second account number;

map the second account number to the first account number; and

transmit the authorization response to an acquirer financial institution with the first account number substituted for the second account number in the authorization response.

7. The storage device system of claim 6 , further comprising

instructions configured to cause the processor to transmit the second account number as auxiliary data in the authorization response transmitted to the acquirer financial institution.

8. The system of claim 6 , wherein the second account number transmitted to an issuer financial institution is a primary account number that identifies a payment card account.

9. The system of claim 8 , wherein the proximity payment device is associated with the payment card account, and wherein the first account number is assigned to said proximity payment device.

10. The system of claim 6 , further comprising instructions configured to cause the processor to transmit the first account number as auxiliary data in the authorization request transmitted to the issuer financial institution.