A banking group claims in a court filing that the data breach at TJX affected about 65 million Visa account numbers and about 29 million MasterCard numbers, roughly twice that the company acknowledged earlier. Supporting their allegations, the banks cited sealed testimony taken from officials at the two largest credit card networks.

The banks want to recuperate the fraud losses from retail giant TJX and want the federal judge in Boston to grant the banks' motion certification as a class of plaintiffs. "Large banks generally devote considerably more resources to payment card fraud management than do smaller banks [...] which technology in turn enables them to react more flexibly to data compromises than small community banks sometimes do," TJX's filing states.

The breach was first announced on January 17, 2007. However, the company discovered the breach in mid-December 2006, which affected credit card, debit card, check, and merchandise return transactions. Personal information such as social security numbers and driver's license numbers from 451 thousand customers were also apparently downloaded by the intruders. The delay in announcing the breach was requested by law enforcement officials.

TJX previously claimed about 75 percent of the compromised cards were expired or had data in the magnetic strip scrambled. Last month, Canadian privacy officials concluded an eight-month investigation which found TJX guilty of negligence, as apparently he intruders gained access to customer information via wireless local area networks at two Marshalls stores in Miami.

The TJX Companies, Inc. is apparently the largest international apparel and home fashions off-price department store chain and can be traced back to 1956' Zayre discount department store chain. In the United States, it operates T.J. Maxx, HomeGoods, Marshalls, A.J. Wright, Bob's Stores and The Maxx stores. In Canada the chain consists of Winners and HomeSense.