One in five employees has altered the security settings on their PC so they can access unauthorised websites, according to a new survey.

Insight Express surveyed 1,000 IT professionals and 1,000 employees across ten different countries including the UK and the US as part of the Cisco Global Security Study, designed to pinpoint the causes of security and data leaks.

The survey revealed that 70 percent of IT professionals admitted staff accessing unauthorised applications and websites had been the cause of around half of their companies' data loss incidents.

A number of other potentially hazardous practices were identified in the research. One in three employees admitted to leaving their computers logged on and unlocked when they're away from their desk, while 66 percent said they use their PCs daily for personal use such as music downloads, shopping and banking. 44 percent of those surveyed also revealed they share their work devices such as laptops and Blackberrys with non-work people, without supervision.

"There were a couple of surprises in the study," admitted John N. Stewart, chief security officer at Cisco. "Even in today's day and age, you can surprised by the most basic security lapses."

"Data protection requires teamwork across the company. It's not just an IT job anymore," Stewart added.