These days, it seems there is no limit to what cyber-criminals can do, and as surprising as it may sound, grocery stores made no exception on hackers’ list. Hannaford Bros. reported an attack on their computer network in Maine earlier this month, adding that 4.2 million credit cards might have been compromised.

In a letter to the customers, Hannaford President and CEO Ron Hodge apologized for the concerns and inconvenience caused, and said that security measures were taken so as to avoid similar attacks in the future. The data theft took place between December 7, 2007 and March 10, 2008, and exposed all Hannaford clients that used their credit or debit cards to make payments.

The theft was possible through malicious software that sent data to the thieves every time a debit or credit card was being used from all the stores of the company’s chains. The data was sent to a processor in Denver and then sent to a provider outside the US, the Wall Street Journal reported. “It was a novel and sophisticated attack on our computer network,” Carol Eleazer, Hannaford Vice President of Marketing, said to the newspaper.

Ever since the attack, 1,800 fraud cases have been reported, all involving credit cards that have been exposed to the thieves between December and March. The company advised its customers to revise their financial institution and credit card statements and report any suspicious charges, adding that “at the time of this potential exposure, Hannaford was certified to be in compliance with the highest security standards required by the credit card industry.”

However high those standards may have been, it looks like nothing gets in the way of hackers when they put their mind to something. Experts warn that this incident was just the beginning for this year and that the phenomenon continues to grow and becomes harder to contain.