Late on Friday afternoon, Sears Holdings Corp. (NASDAQ: SHLD) announced that its Kmart stores had detected an attack on the store’s payment data systems. The company said that the breach began in early September and its systems were “infected with a form of malware that was undetectable by current anti-virus systems.” The company said it has been able to remove the malware.

Sears also said that it believes that “certain debit and credit card numbers have been compromised,” but there is some good news.

Based on the forensic investigation to date, no personal information, no debit card PIN numbers, no email addresses and no Social Security numbers were obtained by those criminally responsible. There is also no evidence that Kmart.com customers were affected.

Sears did not provide an estimate of how many records were compromised, but the company is offering free credit monitoring protection for customers who shopped at the stores with a debit or credit card during September and through October 9.

The largest retail breach ever occurred earlier this year after an attack on Home Depot Inc. (NYSE: HD) compromised 56 million debit and credit cards. Last week JPMorgan Chase & Co. (NYSE: JPM) reported that 76 million households and 7 million small businesses were put at risk following an attack on the bank’s systems. So far in 2014, nearly 77 million records have been compromised.

Such incidents can be very costly to the companies involved. Target Corp. (NYSE: TGT) has recorded $146 million in expenses through early August as a result of an attack on that store’s records that resulted in 40 million accounts being stolen. The total includes an estimate on claims that Target expects will be made on it by the credit card companies, according to a report at Bloomberg News.

Sears stock dropped nearly 6% on Friday to close at $24.78, in a 52-week range of $24.10 to $67.50. Shares regained 5% in after-hours trading, ending the day at $26.00.

ALSO READ: Nearly 77 Million Records Compromised to Date in 2014

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