Dive Brief:

• Neiman Marcus said Jan. 23 thieves installed malware to access cards from July 16 to Oct. 30. MasterCard, Visa, and Discover notified the retailer that 2,400 cards used at Neiman Marcus and Last Call were fraudulently used as a result.

• The Dallas-based retailer said the breach was worse than that and worse than first reported, with 1.1 million credit and debit cards accessed by hackers.

• The latest disclosure comes as the U.S. Federal Bureau of Investigation sent a confidential, three-page warning to retail companies of the dangers of  "memory-parsing" malware in point-of-sale (POS) systems.

Dive Insight:

Neiman Marcus has seemed hesitant to come forth with all information about this breach, but this latest news and the FBI's report are further indications of the risks that malware incursions into store payment systems pose to retailers. Authorities and retail companies continue to worry that these issues at Neiman Marcus and a similar one at Target could be just the tip of a worrisome iceberg. Better security at checkout is clearly a priority for retailers in the U.S. as they strive to ensure their customers that they can use their credit and debit cards with a sense of security.