The increase was revealed in data gathered across more than 100 countries and millions of employees.
Employees tend to assume they can use the internet at work in exactly the same way as they use it at home, said Spencer Parker, product management director at ScanSafe.
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"Inappropriate internet use in the workplace can put the employer at risk for legal liabilities," he said.
Downloading illegal content is a "double whammy" for employers as it puts them at risk legally and puts the company network at risk, said Parker.
"Free illegal downloading websites are often riddled with malware, which could infect corporate networks," he said.
Organisations should implement a comprehensive web security system to block employees from accessing illegal websites, said Parker.
Security consultants have identified employee education as a top priority for businesses in 2010.
Businesses should also ensure internet usage policies are up to date and that employees are aware of what they are not allowed to do at work.
Increased use of consumer devices such as iPhones is another key reason businesses should keep their IT polices and standard up to date, said William Beer, information security director at PricewaterhouseCoopers.
"Employees need to be aware of how their actions can impact on the organisation they work for, but not many businesses have a comprehensive set of policies and an education programme in place," he said.