In our previous blog post "Inside the Attacker's Toolbox: Botnet Web Attack Scripts" we analyzed some botnet scripts that SpiderLabs Research team had captured that are used to conduct massive attack scanning traffic. In this installment, we will take a look at a php script that is used by Botnet owners to validate credit card data that has been illegally obtained.
Targeting Visa, Mastercard and American Express Credit Cards
Here is a snippet of code the shows the functions for checking Visa, Mastercard and American Express credit cards:
Initiating CC Validation
Here is a snippet of code that shows the IRC botnet command (!CHK) used to check various CC dta including the number itself, expiration code and CVV data:
CC Validation Checks
The botnet CC validation functions will pass the data to the botnet clients and instruct them to make HTTP requests to a hacker owned web interface (called /mirc/check.php?cc=) on the 188.8.131.52 host below:
The URL is not currently active and returns 404 errors. Since we could not interact with this resource, it is assumed based on the program work flow, that the check.php file takes the CC data and will execute some type of micropayment transaction to validate the data.
CC Validation Return Codes
Based on the "ssl_avs_response" code within the script, it appears that the scripts are utilizing VirtualMerchant API code. The responses from these API calls are then parsed and validation errors are presented to the attacker:
And another section of validation errors:
Based on the results of these CC validation calls, the attacker will then know if they have legitimate CC information which they can then turn around a sell it on the black-market.