Percentage of companies that report systems hacked

More than 80 percent of U.S. companies have been successfully hacked, according to a Duke University/CFO Magazine Global Business Outlook Survey released on Friday.

The survey was released on the heels of news of a breach of millions of records maintained by the federal Office of Personnel Management.

Successful attacks by hackers involved stealing, changing or making public important data, according to the survey. Smaller companies (those with fewer than 1,000 employees) were more vulnerable, with 85 percent saying their information systems had been broken into. About 60 percent of larger companies reported successful hacks.

"Corporate America is an easy mark for hackers as we are repeatedly reminded in the news," John Graham, director of the survey and a professor at Duke University's Fuqua School of Business, said in a statement. "However, it is not just big firms like Target that are being hit - 85 percent of smaller firms are also under siege. No one appears safe. The situation may even be worse than reported because many firms might not even realize that they have been attacked."

Graham explained smaller firms are more vulnerable because they don't devote as much resources to protect their data. The survey showed that smaller firms were half as likely to take certain extra steps to block hackers, including trying to break into their own systems, hiring staff to protect data or requiring extra training of staff.

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    Mitch Lipka is an award-winning consumer columnist. He was in charge of consumer news for AOL's personal finance site and was a senior editor at Consumer Reports. He was also a reporter for The Philadelphia Inquirer and the South Florida Sun-Sentinel, among other publications.