More than half of people take company information with them when they leave an employer, the US-based Ponemon Institute has found.
The institute interviewed nearly 1,000 Americans who had been laid-off, fired, or changed jobs within the last year.
They said they took the information to help them in getting another job, to help start their own business, or revenge.
The data included proprietary information such as customer data, employee information, financial reports, software tools and confidential business documents.
Only 15% of employers checked what documents and files staff took with them when they left.
Eugene Schultz, a researcher with the Sans Institute, said the study did not show how badly employee's can behave when a company folds.
"I have heard numerous accounts about computer crimes (including brazen thefts of servers) by ex-employees that ostensibly occurred after High Tower Software collapsed," he said. Despite many reports of such illegal activity, no complaints were filed with police.