US retail giant Target announced Monday that chief executive Gregg Steinhafel was stepping down, nearly five months after hackers stole personal data on more than 100 million customers. Steinhafel, chief executive since 2008, will resign immediately as chief executive and chairman of the board. Chief Financial Officer John Mulligan has been appointed interim chief executive, the company said. "After extensive discussions, the board and Gregg Steinhafel have decided that now is the right time for new leadership at Target," the company said in a statement. Target in December disclosed that hackers successfully infiltrated the company's information systems, obtaining credit card data for some 40 million customers. In January the company said an additional 70 million customers could have been affected by a second breach that included names and contact details. The data breach, one of the biggest in retail history, hit company sales during the critical holiday shopping period and spurred congressional hearings on the vulnerability of customer information in an era of increasingly sophisticated hacking efforts. In the wake of the breach Steinhafel quickly moved to shore up customer confidence, green-lighting plans to provide free credit monitoring and identity-theft insurance to shoppers. "Gregg led the response to Target’s 2013 data breach. He held himself personally accountable and pledged that Target would emerge a better company," the company said. Last week Target recruited a new executive vice president in charge of information technology transformation, and said it continues to search for a new chief information security officer. Target said Monday that board member Roxanne Austin will serve as interim non-executive chair of the board. In addition, Steinhafel has agreed to serve the company as an advisor during the transition.