A major loss of customer information is expected once every five years, according to 59 per cent of businesses.

The average incident exposes the data of more than 785,000 customers and causes significant reputational damage, according to the annual IT risk management survey from security supplier Symantec.

“Because customers withdraw from transaction providers and venues they don’t trust, data leakage constitutes a serious threat not only to consumers, but to electronic commerce and banking,” says the Symantec report.

The widespread use of mobile devices will compound the problem, according to Symantec service development director Jeremy Ward.

“The growth in mobile and portable devices makes assets much harder to track and greatly increases risk,” he said.

Nearly two-thirds (63 per cent) of the survey’s respondents believe a data leak would have serious impact on their businesses, and more than half (53 per cent) ranked mobile devices as a serious risk. But only one third (34 per cent) said the business has the ability to manage them.

The use of mobile devices is also placing greater importance on staff training and awareness.

“More process errors than technology glitches are responsible for incidents, which suggests that businesses are not using training schemes properly,” said Ward.

The number of firms rating internal training programmes as “more than 75 per cent effective” fell to 44 per cent, from 50 per cent a year ago.

There is much at stake. According to a survey by the Ponemon Institute, 62 per cent of consumers are more upset with data loss caused by negligence than theft.

Firms should monitor security procedures every one to three weeks, says Symantec.