Nearly a week after this blog first reported signs that Home Depot was battling a major security incident, the company has acknowledged that it suffered a credit and debit card breach involving its U.S. and Canadian stores dating back to April 2014. Home Depot was quick to assure customers and banks that no debit card PIN data was compromised in the break-in. Nevertheless, multiple financial institutions contacted by this publication are reporting a steep increase over the past few days in fraudulent ATM withdrawals on customer accounts.
The card data for sale in the underground that was stolen from Home Depot shoppers allows thieves to create counterfeit copies of debit and credit cards that can be used to purchase merchandise in big box stores. But if the crooks who buy stolen debit cards also are able to change the PIN on those accounts, the fabricated debit cards can then be used to withdraw cash from ATMs.
Experts say the thieves who are perpetrating the debit card fraud are capitalizing on a glut of card information stolen from Home Depot customers and being sold in cybercrime shops online. Those same crooks also are taking advantage of weak authentication methods in the automated phone systems that many banks use to allow customers to reset the PINs on their cards.
Here’s the critical part: The card data stolen from Home Depot customers and now for sale on the crime shop Rescator[dot]cc includes both the information needed to fabricate counterfeit cards as well as the legitimate cardholder’s full name and the city, state and ZIP of the Home Depot store from which the card was stolen (presumably by malware installed on some part of the retailer’s network, and probably on each point-of-sale device).
This is especially helpful for fraudsters since most Home Depot transactions are likely to occur in the same or nearby ZIP code as the cardholder. The ZIP code data of the store is important because it allows the bad guys to quickly and more accurately locate the Social Security number and date of birth of cardholders using criminal services in the underground that sell this information.
Why do the thieves need Social Security and date of birth information? Countless banks in the United States let customers change their PINs with a simple telephone call, using an automated call-in system known as a Voice Response Unit (VRU). A large number of these VRU systems allow the caller to change their PIN provided they pass three out of five security checks. One is that the system checks to see if the call is coming from a phone number on file for that customer. It also requests the following four pieces of information:
-the 3-digit code (known as a card verification value or CVV/CV2) printed on the back of the debit card;
-the card’s expiration date;
-the customer’s date of birth;
-the last four digits of the customer’s Social Security number.
On Thursday, I spoke with a fraud fighter at a bank in New England that experienced more than $25,000 in PIN debit fraud at ATMs in Canada. The bank employee said thieves were able to change the PINs on the cards using the bank’s automated VRU system. In this attack, the fraudsters were calling from disposable, prepaid Magic Jack telephone numbers, and they did not have the Cv2 for each card. But they were able to supply the other three data points.
KrebsOnSecurity also heard from an employee at a much larger bank on the West Coast that lost more than $300,000 in two hours today to PIN fraud on multiple debit cards that had all been used recently at Home Depot. The manager said the bad guys called the customer service folks at the bank and provided the last four of each cardholder’s Social Security number, date of birth, and the expiration date on the card. And, as with the bank in New England, that was enough information for the bank to reset the customer’s PIN.
The fraud manager said the scammers in this case also told the customer service people they were traveling in Italy, which made two things possible: It raised the withdrawal limits on the debit cards and allowed thieves to withdraw $300,000 in cash from Italian ATMs in the span of less than 120 minutes. Continue reading →