New York: More than 40 million credit and debit card numbers have been stolen from nine major stores and restaurant chains across the United States, making it the biggest identity theft case in the history of the US. Feds say the hackers stole tens of millions of dollars from people who shopped at stores like OfficeMax, DSW, Barnes & Noble, Sports Authority, Forever 21, TJ Maxx and Boston market. The alleged criminals sat outside the stories with a laptop loaded with a “sniffer” program to intrude into stores’ wireless networks. "This allowed the defendants to remotely capture sensitive information such as card numbers, passwords and account information,” US attorney Michael Sullivan explained. The hackers allegedly sold that personal information to a third party or used it themselves. Some numbers were stored on magnetic strips of “blank” cards, and used to draw tens of thousands of dollars from ATMs. “This is what you would call a white-collar crime. It’s probably one of the biggest challenges we face in the 21st century, where huge amounts of money move over the Internet," Secretary, Homeland Security, Michael Chertoff says. Many people whose numbers were stolen don't even realise they're victims yet. But Chertoff says they're working with stores to close the cyber holes. "The international system is safe but I also have to tell you the bad guys are smart too," he says.