March 30, 2012 - Visa and MasterCard are warning banks that a US credit card processor has suffered a major security breach that may have compromised the data of millions of people, according to the KrebsonSecurity blog.

Citing sources, the well-connected Krebs says the breach - which happened between 21 January and 25 February - is being called "massive", potentially involving more than 10 million cards.

In alerts to banks, Visa and MasterCard have warned that "full Track 1 and Track 2 data" has been taken, meaning counterfeits could be made using the information. The name of the processor has not been revealed.

Update 1: MasterCard has confirmed that it is investigating a breach at a third party processor. The card scheme says police and the Secret Service have been notified and that a forensic investigation is underway at the unidentified third party. The company declined to say how many cards had been hit by the incident.

Update 2: US card processor Glbal Payments has confirmed in a press release late Friday evening that it discovered an unauthorised access of its processing system in early March.