It's the last thing cash-strapped banks need right now: Holders of credit and debit cards are reporting an epidemic of unauthorized charges on their bills. It could be the sign of a massive card-fraud operation in the making. A company called Adele Services, based in Melville, N.Y., has been charging cards small amounts — 21 to 29 cents. Such charges are usually attempts by card fraudsters to test whether a particular card number is valid.

The range of complaints suggests the people behind the Adele charges have gotten their hands on a sizable database of credit cards. Large-scale hacks have happened before; the worst was in 2005, when hackers obtained a file of 40 million card numbers from CardSystems, a credit-card processor. While most consumers worry about shopping with Internet retailers, online card databases are rarely the problem. Last year, insecure cash registers at TJ Maxx and Marshalls stores exposed 45.7 million cards.