Microsoft is expanding a program to defend customers of its cloud-computing services from copyright lawsuits filed by patent trolls and other companies.

Microsoft's customer agreements already included a pledge from the Redmond company to defend users of its Azure cloud-computing platform in cases in which third parties claim that the use of Microsoft's software infringed on their patents.

That plan will expand to cover the open-source software sold on Azure, Microsoft President and Chief Legal Officer Brad Smith [pictured here] said in a blog post Wednesday. The company will also offer customers who are sued for use of Azure the aid of 10,000 Microsoft patents in their defense, Smith said.

Microsoft is eager to differentiate itself from its larger rival in the cloud world, Amazon.com, by bolstering its promises to secure customers' data and defend them from legal complications.

Cloud-computing, the fast growing business of selling on-demand computing power and data storage, is increasingly a target of patent trolls -- companies that hoard patents for the purpose of lucrative intellectual property lawsuits -- Microsoft says.

Smith in a blog post Wednesday cited a Boston Consulting Group (BCG) study showing that companies that purchase patents without the intent to develop them are increasingly buying cloud-computing patents. Intellectual property lawsuits relating to the cloud are up 22 percent in the last five years in the U.S., the company said, citing BCG.

Microsoft decided to expand its indemnification policy following cases in which financial institutions asked Microsoft for help defending against patent lawsuits related to work on Azure, the company says.