According to the company, only the numbers and expiration dates of the credit and debit cards could have been accessed, and no other customer data -- such as names and addresses -- was taken. So far, the investigation has determined that the attackers got their hands on cards used between December 2012 and March 29, 2013, at 79 of the company's more than 90 stores.
The situation came to the company's attention March 15 when a credit card processor noticed that 12 cards used at Schnucks stores had been used to commit fraud. The company immediately began to investigate, ruling out employee misconduct and any tampering with point-of-sale devices.
By March 19, more incidents of fraud were reported, prompting Schnucks to organize an incident response team. The company commissioned Mandiant to help with its investigation and the following day contacted law enforcement. On March 28, Mandiant identified the malware used by the attackers; in the next two days, Schnucks implemented a containment plan and admitted the attack.
"We've worked hard to provide a secure transaction environment for our customers and, today I make a personal pledge to you that we will be relentless in maintaining the security of our payment processing system," said Schnucks CEO Scott Schnuck, in a statement. "We expect that the actions we have taken and will take in the future will send a clear signal that our customers may continue to trust us."
The company has worked with the payment processor to make sure any card numbers potentially affected were sent to the credit card companies so that they may send alerts to the issuing banks, according to the grocery store chain.
"While PCI-DSS has helped protect merchant environments through security requirements and audits, it is usually difficult to provide perfect security," says Jose Diaz, director of technical and strategic business development at Thales e-Security. "PCI-DSS and best practices can help mitigate risk but not necessarily completely eliminate it due to the complexity of some environments.
"One of the approaches to improve a security posture is to scope reduction. If the sensitive data in merchant environments can be isolated, it will be much easier to protect. Attempting to protect complete IT infrastructures can be a very complex task."
Schnucks contacted the Secret Service and FBI about the incident.
"On behalf of myself, the Schnuck family, and all of our 15,000 teammates, I apologize to everyone affected by this incident," Schnuck said. "Over the years, technology has helped us deliver superior customer service, but it also introduces risks that we have actively worked to manage through compliance audits, encryption technology and various other security measures."
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