It is the largest case of identity theft in the country. More than 41 million credit and debit card numbers were stolen by an international ring that hacked into the computer networks of nine national retail chains, including Barnes & Noble, BJ’s Wholesale Club, OfficeMax and TJX Cos.

This week’s indictments serve as a warning to consumers. But they also can serve as a reminder to take a few simple steps to protect yourself from this kind of crime, which affects as many as 8 million Americans each year, costing billions of dollars and countless hours to correct the problems it creates.