Microsoft Corp. has filed 26 lawsuits accusing U.S. companies of selling pirated software, the latest move in its ramped-up efforts to boost sales by cracking down on illegal copies.

The world’s largest software maker filed the lawsuits Friday in federal courts in Georgia, Illinois, Ohio, Colorado, South Carolina, New York and New Jersey. The lawsuits accuse the companies of selling illegal copies of its Windows operating system and Office business software.