Credit card thieves are becoming big-time charity donors, but it's not out of the goodness of their hearts. According to Symantec Corp. the criminals are starting to use charitable donations as a way to check whether their stolen credit card numbers are working.Credit card numbers are bought and sold in underground "carder" forums, which bring together the people who have stolen the credit card numbers with those who want to use them. These charitable donations are typically made by the person buying the card numbers as a final check to ensure that the numbers will work.Symantec's security response weblog noted the interesting trend, where scammers will use charities to test if a card is active without raising suspicion.Identity thieves frequently test credit card information by moving small sums of money, and banks have responded by scanning transactions records looking for unusual recipients of what look like test transactions.Even if the charity test is performed on just a small fraction of stolen card numbers, the contributions could add up. The Federal Trade Commission recorded 670,000 cases of reported identity theft and fraud in 2006, 60% of which began with Internet solicitations. And corporate breaches spill millions of customers' credit card information into the black market: A breach in January at the retailer TJ Maxx revealed the private financial data of more than 46 million customers, while Certegy Credit Systems, a branch of Fidelity National Information Services, announced last week that a former employee had stolen and sold customers' data, exposing as many as 2.3 million accounts.Given that Symantec's researchers see the charity test as a growing trend, the tactic could mean significant sums of money moving into philanthropic coffers, if only in $5 and $10 increments.