NEW YORK (CNN) -- A hacker has gained access to as many as 2.2 million Visa and MasterCard accounts, the two companies announced Monday.
The hacker breached the security system of a company that processes credit card transactions on behalf of merchants, Visa and MasterCard said.
None of the Visa accounts has been used fraudulently, Visa spokesman John Abrams said.
The affected accounts make up about one-third of 1 percent of the 560 million MasterCard and Visa cards in the United States. Spokesmen for the two companies said they have notified the banks that issued the affected cards.
MasterCard and Visa would not disclose how many banks they had notified, nor would they say whether the hack was a regional or national problem.
