LONDON, March 16 (Reuters) - The chief executives of some of the worlds' leading private companies are confident about their firms' prospects and plan to recruit more staff, but are ill-prepared for cyber attacks, according to a report by PwC on Thursday.

The "Undaunted, but underprepared?" report found 86 percent of CEOs were confident about their companies revenue prospects in 2017, an increase of 5 percent from last year.

That made it the first time in five years that private company bosses were more confident than public company CEOs.

The report, based on responses from 781 private company CEOs in 79 countries, also found that 41 percent of private company CEOs were not concerned about cyber threats and only 68 percent were concerned about the speed of technological change.

Stephanie Hyde, Global Entrepreneurial and Private Business Leader for PwC UK, said it was worrying that private company CEOs were less concerned about technology and cyber compared to their public counterparts, as they had less resources available to invest in addressing these issues.

"This may make them more vulnerable to cyber attacks, so in theory they should be more concerned about these threats not less," she said.

"In our view, this is probably the single most worrying finding in our report, especially in light of growing evidence that hackers are now targeting smaller and private businesses, thinking they will not be so well protected." (Reporting by Michael Holden)