Bangalore: Zappos.com the online shoe retailer, and its discount shoe store 6PM.com, which are both owned by Amazon, sent an email to its customers over the weekend, stating that it might have experienced an unauthorized breach of customer data.

The website, in an email to its customers, stated that customers’ names, billing addresses, email addresses and phone numbers, along with the last 4 digits of credit card numbers, and cryptographically scrambled passwords (not the actual passwords) might have been available to the hacker(s). The email also maintained that the database that contained critical card information and transaction details had not been affected in any way.

The websites proceeded to change the passwords of all users, and sent them all emails with the reset passwords, along with steps to change the passwords to their choice. Zappos advised customers to change their passwords in case they had used the same on other sites.  Around 24 million customers have been affected by the breach.

Zappos chief executive Tony Hsieh said the companies were “cooperating with law enforcement to undergo an exhaustive investigation." In a company-wide memo, CNN Money reported Hseih saying "We've spent over 12 years building our reputation, brand and trust with our customers. It's painful to see us take so many steps back due to a single incident."

The hack that Zappos experienced, however, was not even close to the scale of those experienced by companies in the past. Sony was hacked thrice within a span of three months last year, and 77 million of its customers had their credit cards information stolen.

The first international data-breach that involved credit card information was carried out in 1995, with $3.7 stolen from CitiBank and distributed to the members of a Russian team under Vladimir Levin. Levin, who was a mathematician as well as a graduate in biochemistry from the St. Petersburg Tekhnologichesky University, conducted 18 different attacks to acquire the sum. He was eventually caught and almost all the money was restored according to the International Business Times.