In the wake of a breach at Target last December that exposed the credit card information of 40 million customers and the personal data of millions more, the industry pledged to move quickly and aggressively to protect customer data.  But experts say the latest breach shows that many retailers likely remain vulnerable to hacks.

"The biggest challenge in today’s environment is the hackers are getting better," said Chuck Winter, a consultant with North Highland Co., who has developed information technology strategies for retailers. "We've seen the complexity of the retailers' technology platforms make it challenging to completely secure their total environment."

On Tuesday, a coalition of state lawmakers announced that they would be investigating the Home Depot breach.  Meanwhile, Sens. Edward J. Markey (D-Mass.) and Richard Blumenthal (D-Conn.) sent a letter to FTC chairwoman Edith Ramirez asking the agency to probe the hack at Home Depot.

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