NEW YORK - Add hackers to the long list of things that give CEOs insomnia.

Target's chief executive, Gregg Steinhafel, is the first boss of a major corporation to lose his job over a theft of customer data. His exit from the helm of the nation's second-largest retailer on Monday shows that - in addition to guiding company strategy and keeping Wall Street happy with ever-growing profits - today's chief executives are being held responsible for lapses in computer security.

Daniel Ives, an analyst for FBR Capital Markets, believes many CEOs will be placing calls to their chief information officers, just to make sure their operations are as fortified as possible.

Steinhafel was in charge when hackers stole millions of consumer data records, including credit card number, names and addresses, from Target's computer system last holiday season.

To be sure, Target had been struggling with weak sales for several years and had run into problems with its Canadian expansion. But there's no denying the breach and its fallout were big factors in Steinhafel's departure, says Ronald Humphrey, a professor who studies leadership at Virginia Commonwealth University.

"This is a wakeup call to CEOs that data security is something that affects their customers," Humphrey says. "If you've had your identity stolen, you know it's a huge headache. I think they have to take this very seriously."

Minneapolis-based Target Corp.'s computer systems were infiltrated by hackers who took 40 million debit and credit card numbers, along with the personal information of as many as 70 million people.

Investigations by both Target and the Secret Service are ongoing. Neither has released details about their probes and the Secret Service has said it could take years to bring the responsible parties to justice.

Target's revenue, earnings and stock price have all suffered since the breach's disclosure in December.

Robert Hurley, a professor of management at Fordham University, says recent weak store traffic and the company's problems in Canada were probably equally big factors in the Target board's weighing of Steinhafel's fate.

But Hurley adds that the breach was a major event that damaged Target's reputation and credibility with customers. That damage likely prompted the board to act. Hurley credits the board with taking its time and not making a knee-jerk decision.