and push their cars. An inch of rain in six minutes. Tonight new concern about a security breach, this time at Home Depot, and it could be bigger than the breach at target. In that case 40 million... See More
and push their cars. An inch of rain in six minutes. Tonight new concern about a security breach, this time at Home Depot, and it could be bigger than the breach at target. In that case 40 million customers, their credit card information stolen. How the Numbers could be even larger this time, and what should you do? ABC's chief business correspondent Rebecca Jarvis now. Reporter: Tonight Home Depot confirming they're working with banks and law enforcement that could put millions of people's credit card Numbers in the hands of criminals. We know that the sale of both credit and debit card Numbers are preceding in the black market. Reporter: The potential breach involving all of home Depot's stores and possibly online purchases would likely be even bigger than the attack over the holidays on target when thieves made off with 40 million credit cards. Security experts say the best way to reduce this fraud, embedding chips like this one into credit cards. American retailers plan to launch that technology next year, but it's already in use in Europe. When they introduced chip in pin cards in Europe, it decreased the amount of instore fraud by 60%. Over 60%. Reporter: It's not a silver bullet. With 226 million Americans shopping online each month. Bottom line on that is that chip and pin is not going to help you online. Reporter: So how can you protect yourself now? Consider using apps like bill guard which monitor your accounts 24/7 for fraudulent charges. Home Depot tells us they are rapidly gathering facts. They will immediately notify customers. No one will be responsible for fraudulent charges on their account and Home Depot will offer free services for identity theft protection to anyone impacted. Thank you.
This transcript has been automatically generated and may not be 100% accurate.