B&N said it's continuing to work with federal law enforcement and with banks, payment card brands and issuers to identify accounts that may have been compromised, so that additional fraud-protection measures can be taken.
Customers at its book stores will now have to ask cashiers to swipe credit or debit cards on card readers connected to cash registers, a process that is secure, Barnes & Noble said.
Anything bought on Barnes & Noble.com or with the chain's Nook devices and app were not affected, the company said. It also said its customer database is secure.
Barnes & Noble is only the latest major retailer to be a victim of a serious data breach. In one of the largest, more than 45 million credit and debit cards were exposed to possible fraud because of hackers who broke into the computer system of TJX Cos., the parent company of retailers T.J. Maxx and Marshall's, starting in 2005.