WASHINGTON D.C. -- Target executives were back on the hill Wednesday testifying in front of a house committee about the security breach that left millions of shoppers with compromised credit cards.

Tuesday committee members came up with possible solutions to prevent future breaches including special smart chips on cards that are more secure than magnetic strips.

Wednesday, house members grilled the United States Secret Service about why the hacker’s malware was so destructive.

"What makes these targeted attacks unique is that the criminals are modifying and molding specific types of malware to fit whatever network or intrusion set they're going after," said Secret Service Agent William Noonan.

Between Thanksgiving and early December hackers stole information from Target on 40-million customer credit cards and personal data on 70-million Target customers.