Target said Thursday it investigated but ultimately dismissed early signs of a data breach, a decision it likely regrets after suffering one of the largest payment-card and personal-data breaches on record.
The retailer said it logs a vast number of technical events each week, and "a small amount of [the criminals'] activity was logged and surfaced to our team. That activity was evaluated and acted upon," Molly Snyder, a Target spokeswoman, said in an emailed statement on Thursday.
"Based on their interpretation and evaluation of that activity, the team determined that it did not warrant immediate follow up," Snyder wrote. "With the benefit of hindsight, we are investigating whether, if different judgments had been made the outcome may have been different."
The breach of Target's network resulted in the loss of 40 million payment card details, plus 70 million other personal records, causing U.S. lawmakers to question whether companies are doing enough to protect personal data. Target's data was stolen between Nov. 27 and Dec. 15, the busiest shopping period in the U.S.
Snyder wrote that despite investing hundreds of millions of dollars in security, "the unfortunate reality is that we experienced a data breach."
She declined to provide a timeline for the early clues, but said the retailer was notified by the U.S. Department of Justice of a possible breach on Dec. 12. Target confirmed the breach three days later.
Target's cash registers, known as point-of-sale (POS) terminals, were infected with a type of malware called a "RAM scraper." The malware recorded payment card details after a card was swiped and the unencrypted data briefly sat in a system's memory.
Security experts believe a variant of "Kaptoxa," also called "BlackPOS ," was used against Target. The malware was spotted by security companies as early as March 2013.
The style of attack, which also affected luxury retailer Neiman Marcus, was notable for finding weaknesses despite a long-running effort to implement better security around card handling with the Payment Card Industry's Data Security Standard (PCI-DSS).