Testifying before the Senate Judiciary Committee hearing Tuesday, an executive for retail giant Target apologized for the data breach which compromised the credit and debit card data of 40 million Target customers.

"I want to say how deeply sorry we are for the impact this incident has had on our guests, your constituents," John Mulligan, executive vice president and chief financial officer for Target, said. "We know this breach has shaken their confidence in Target, and we are determined to work very hard to earn it back."

Mulligan, who testified alongside Michael Kingston, senior vice president and chief information officer for The Neiman Marcus Group, said the store remains committed to enhancing security measures to ensure another breach does not occur.

The company is undergoing an end-to-end review of its network, has increased fraud detection for its Target REDcard users and has reissued new Target credit or debit cards to any users that request one, Mulligan detailed. Target is offering one year of free credit monitoring and identity theft protection to any customer who has shopped at Target stores.

Target, which first disclosed the company's data breach Dec. 19, is ramping up its investment in chip technology for its Target REDcards and point-of-sale terminals in its stores.

"We believe that chip-enabled technologies are critical to providing enhance protection for consumers," Mulligan said.

Kingston said payment card transactions at 77 of Neiman Marcus' 85 stores may have been exposed between July and October of 2013. Neiman Marcus has previously estimated 1.1 million accounts may have been compromised.

Sen. Patrick Leahy, chairman of the Senate Judiciary Committee, said it's critical for stores to improve its security protections and move quickly to inform consumers of potential breaches.

"Public confidence is crucial to our economy," Leahy said. "If consumers lose faith in business' ability to protect their personal information, our economic recovery will falter."