Nightly News   |  December 19, 2013

How thieves use your personal data

‘Track data,’ which includes the names, dates, numbers and codes stolen from credit and debit cards, can be used to make purchases online or create new, fraudulent cards. NBC’s Stephanie Gosk reports.

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This content comes from Closed Captioning that was broadcast along with this program.

>>> this is stephanie gosk in new york. roughly tens of millions of credit and debit cards are potentially compromised. names, numbers, dates and codes. it's what security officials call track data. hackers steal the it and criminals known as carders are already waiting to buy it. a well established black market network.

>> professionals that have been doing it for 10, 15 years already have the carders in place.

>> reporter: kevin mandy started the firm mandiant in 2004 . the the chinese army launched cyber attacks against dozens of u.s. companies for years.

>> there are people on a daily basis waking up trying to break into your networks. right now it is exceptionally complicated to defend your network.

>> reporter: track data can be used in multiple ways. carders will try to make purchases online. others may make fraudulent cards or what's called cloning. "wired" magazine showed how easy it is to print a card.

>> swipe the card through.

>> reporter: security experts point out that not all the track data is useable. cards expire, personal information changes.

>> you go to the remainder and it is how they are used. whether they are sold to people or get in the hands of carders who are good and aggressive.

>> reporter: a number of retailers have been hacked. in 2007 , 90 million cards were stolen from tjx which owns tj maxx and home goods. foreign hackers were accused of stealing credit card numbers from retailers including 7-11, jetblue and jc penney . security experts say it might be just the first shoe to drop. that other big retailers are having issues. one of the difficulties in tracking down hackers is many of the large rings are overseas and the u.s. has little authority to go after them.

>> stephanie gosk and tom costello on the lead story tonight.