In an interview with CNBC, Target chairman and CEO Gregg Steinhafel revealed "there was malware installed on our point-of-sale registers" which has since been removed.

The malware enabled crooks to steal the details of around 40 million customer cards and the personal information - including names, mailing and e-mail addresses, and phone numbers - of another 70 million.

While Target is working with law enforcement agencies to figure out how the attack was conducted and who was behind it, a massive damage limitation campaign is also underway in a bid to assure customers that it is safe to shop at the retailer.

Full page adverts have been taken out in major newspapers apologising for the breach, with Steinhafel vowing: "We are determined to make things right, and we will."

The company has also committed $5 million to set up a coalition dedicated to educate consumers about cybersecurity and the dangers of phishing scams. The National Cyber-Forensics and Training Alliance, National Cyber Security Alliance and Better Business Bureau have all signed on.

The fall out from the breach is likely to hit target hard, with Putnam Bank the first to file a suit against the chain, claiming that the security breakdown forced the bank to issue customer alerts and new cards, while reimbursing account holders for losses. Separately, JPMorgan has confirmed that it replaced two million customer payment cards in the wake of the breach.

Meanwhile, House of Representative Democrats have called for a congressional inquiry into the data breach. Following the lead of Senate colleagues, 17 Democrats wrote to Financial Services Committee chairman Jeb Hensarling, asking for the hearing.

In a statement, Hensarling says: "The House Financial Services Committee has held, and will continue to hold, hearings on the security of information collected by these agencies and financial institutions and will continue to press for accountability of all those who collect personal consumer data."

In the last few days it has emerged that Target is not the only retailer to have been hit by hackers in recent weeks. Neiman Marcus Group has admitted that crooks have compromised its systems and made off with customer card details, while several other merchants are reported to be preparing to go public with their own breaches.

The news has led to calls for an industry-wide switch to chip-based EMV cards in the US, with MasterCard the latest to weigh in. In a a letter to financial institutions, merchants and other customers, Chris McWilton, MasterCard president, North America, outlined the company's commitment to maintaining the current timeline and liability shift milestones for the U.S. EMV-Chip migration. 

While there has been some questions on how the current uncertainty regarding US debit routing requirements may impact the implementation of EMV, McWilton outlined the need to maintain progress toward the upgrade of the US market that will "drive both innovation and security for all of us and, more importantly, consumers and cardholders…As we've seen recently, the fraudsters will not delay their activities."