The theft earlier this year of thousands of credit card records from the nation's third-largest warehouse club illustrates the potential for massive-scale identity theft whenever so much purchase-enabling information is stored in one place. It also illustrates how difficult the cleanup can be.

The Secret Service still doesn't know whether the breach was an inside job or the work of hackers, but it has made some arrests, said Tim Buckley, a Secret Service agent investigating the case.

The suspects arrested recently in the United States and abroad may have ties to a large international identity theft ring, Buckley said. He declined to say how many arrests have been made or provide further details.

Meanwhile, financial institutions are still smarting. They've had to reissue hundreds of thousands of credit cards belonging to BJ's customers as a precaution against further fraud.