Microsoft has launched a Halloween blitz on software pirates dealing in what it describes as counterfeit "trick" software disguised as genuine code.

The Redmond giant has filed 20 lawsuits against alleged dealers of counterfeit or infringing software in Alabama, California, Connecticut, Georgia, Illinois, Mississippi, New Jersey, New York, Ohio, Oklahoma, Texas, Utah and Virginia.

Microsoft said that the lawsuits are part of its ongoing commitment to protect intellectual property, jobs, honest resellers and partners. It added that much pirated software leaves users open to viruses, loss of data or identity theft.

"This is not just about protecting Microsoft's intellectual property," said Microsoft attorney Sharon Cates.

"This is also about protecting consumers and the thousands of owners of small and large businesses and their employees who make up the software industry and depend on it for their livelihoods."

A recent Gallup study commissioned by the US Chamber of Commerce found that 22 per cent of adults in the US have reported purchasing some type of counterfeit product in the past year.

Counterfeit products range from auto parts to cigarettes, and from extension cables to software.