One notorious incident involved retail giant TJX. In that case, hackers stole some 46 million credit and debit card numbers when they accessed the computer systems at two TJX corporate hubs over a period of several years. By some estimates, the intrusion was the biggest breach of personal data ever reported.
TJX officials reported that unauthorised software placed on its computer systems stole at least 100 files containing data on millions of accounts from systems that process and store transaction information in those two locations. TJX officials believe the hackers were able to steal payment card data from one system as transactions were being approved. The hackers may have had access to the company's data encryption tool.
