On Dec. 23, the last thing holiday shoppers at Target wanted to be thinking about was having their credit-card information compromised. But that was one luxury no one on hand could afford.

“We don't know yet,” one harried store manager in Staten Island painfully admitted to one especially persistent elderly woman demanding answers about what data thieves now knew. Was she safe? Could she continue to shop? Should she? How badly had the retail giant's consumer database been compromised? No one could say for certain.

Target's data breach, involving the theft of at least 40 million credit and debit card records and personal information of 70 million customers, dominated headlines after it was publicly revealed in late December 2013, driving home the need for better protections against the growing specter of cyber crime. But if the Target incident was unusually large in scope, it was by no means unique: The Identity Theft Resource Center, which has tracked data breaches since 2005, reported 619 publicly disclosed breaches in 2013—a 30% increase over 2012.