SEATTLE – Microsoft Corp. has filed more than 50 legal actions worldwide against people it says sold pirated copies of its software using online auction sites such as eBay.

The legal actions are the latest in a broad effort Microsoft has taken to curb widespread piracy of products such as the Windows operating system and Office software suite. The moves come as Microsoft is seeing the market for its products become more saturated, leaving the company eager to add revenue by curbing illegal distribution.

Microsoft also is gearing up to release new versions of Windows and Office, which remain Microsoft’s biggest cash cows despite the company’s many other lines of business.

The lawsuits and other actions were being filed Friday, Monday and today in the United States, Germany, France, the United Kingdom, South Korea, Poland and several other countries.

Matt Lundy, a senior attorney with Microsoft’s antipiracy group, said Microsoft works with auction sites including eBay to remove listings for software it believes is pirated and only takes legal action if the merchants continue to sell the software after that.

EBay Inc. spokesman Hani Durzy said he couldn’t comment specifically on these cases because he hadn’t seen the particulars. But in general, he said, eBay works closely with Microsoft and others to remove listings for products that are believed to be pirated.

Still, legal actions aren’t uncommon for the world’s largest software maker. Between July 1 and Sept. 30, Microsoft took legal action about 275 times against various groups it believed were dealing in counterfeit software.