MasterCard Inc., Visa Inc. and Discover Financial Services have been victims of a potential security breach, the latest in a string of incidents that have put the personal information of millions of credit cardholders at risk. The companies - the first, second and fourth largest global credit card processors, respectively - said the issue stemmed from a third-party vendor and not their own internal systems. It is unclear just how large of a breach this is and how many customers might be affected. MasterCard and Visa said they have notified banks about the security breach. Discover said it is monitoring accounts for suspicious activity and will reissue cards “as appropriate.” “MasterCard is concerned whenever there is any possibility that cardholders could be inconvenienced and we continue to both monitor this event and take steps to safeguard account information,” the company said in a statement. “If cardholders have any concerns about their individual accounts, they should contact their issuing financial institution.” Visa said it provided banks with affected customers' account numbers and emphasized that customers are not responsible for fraudulent purchases. The companies' statements came after the blog KrebsonSecurity reported that MasterCard and Visa have been alerting banks across the US about a “massive” breach that may affect more than 10 million cardholders. The report said accounts were compromised between January 21, 2012 and February 25, 2012. JPMorgan Chase & Co. said it has been notified of the breach and is monitoring affected customers' accounts.
