Hannaford Bros – Malware

In 2007, a Russian/Ukrainian hacking gang targeted Hannaford's main servers, successfully spreading malware to all 300 of the company's stores as well as a handful of independent stores that sold Hannaford items. The thieves who stole up to 4.2 million credit and debit card details from Hannaford Bros. Co.'s networks did so by placing malware programs on servers at each of the grocer's stores in New England, New York, and Florida, according to the supermarket.

According to a letter filed to Massachusetts regulators, the malicious software was used to intercept credit card data while it was being transported from Hannaford's point-of-sale systems to approve transactions. According to the letter, which was signed by Emily Dickinson, Hannaford's general counsel, the virus subsequently transferred the stolen card information as well as their expiration dates to an offshore location. 4.2 million Hannaford customer credit card details were taken in the massive data breach, with at least 1,800 of them being used fraudulently. The attack is believed to have cost $252 million (£201 million) in total. It's one of the most expensive cyber attacks in the world.

Cost: £201 million