Visa and MasterCard are warning of what they call a “massive breach” that could involve as many as 10 million compromised card numbers.

The breach occurred between January 21, 2012 and February 25th 2012. They say that this information, known as full Track 1 and Track 2 data, could be used to counterfeit new cards.

They are not saying which U.S based processor was the actual source but the affected banks are now analyzing the data hoping to find points of purchase.

According to KrebsonSecurity:
“It’s not clear how many cards were breached in the processor attack, but a sampling from one corner of the industry provides some perspective. On Wednesday, PSCU — a provider of online financial services to credit unions — said it alerted 482 credit unions that appear to have had cards impacted by the breach, and that a total of 56,455 member VISA and MasterCard accounts were compromised. PSCU said fraudulent activity had been detected on a relatively small number of those cards — 876 accounts — and that the activity was geographically dispersed.”

As always one should be diligent by keeping a secure login to their bank account and other sensitive online financial accounts and check them regularly for anything suspicious. Majorgeeks likes to use RoboForm Everywhere to create secure passwords and login safely. It is free for 30 days and 10 logins but for $9.99 you really can’t beat it for having that extra layer of security online.

Update 1:
There is no mention of whether this is credit or debit cards (just the word "cards") so as of right now we assume this means both.

Update 2:
According to KrebsonSecurity: “Sources at two different major financial institutions said the transactions that most of the cards they analyzed seem to have in common are that they were used in parking garages in and around the New York City area."