Microsoft filed 15 lawsuits on Tuesday — 13 in the U.S. and two in the U.K. — as part of its expanding anti-spam initiative.

The Redmond software giant filed the suits following investigations across 34 countries involving companies and individuals who have sent two billion illegal spam messages to MSN and Hotmail users.

Twelve of the 15 suits were filed in King County superior court under a Washington state anti-spam statute that allows Internet Service Providers (ISPs) to target spammers who send unwanted communications to Washington-based consumers. Another suit was filed in federal court in Los Angeles.

The two civil suits filed in the U.K. focus on spammers who allegedly have attempted to harvest MSN and Hotmail subscriber names from Microsoft's database. The U.S. cases focused primarily on the alleged use of deceptive practices, such as false subject lines, false sender Ids and/or spoofed identities. The California case also involved an alleged violation of the Microsoft trademark.

Microsoft is seeking both punitive and monetary damages of varying amounts in the cases, Smith said.

In evolving its anti-spam campaign, Microsoft is building on its expertise in fighting software piracy and counterfeiting in its anti-spam campaign, said Microsoft senior vice president and general counsel Brad Smith. Smith said to expect the company to bring more cases in more countries around the world in the future.

Microsoft announced the latest twist in its anti-spam initiative via a press conference that was held simultaneously in Redmond, Wash., and London. Washington State Attorney General Christine Gregoire, who attended the press conference, backed Microsoft's play.

"We're pleased to support this announcement by Microsoft," said Gregoire. "Our delete key will not solve this problem," she added. And "government cannot solve this problem alone."

Microsoft has been stepping up its publicity campaign around its four-pronged approach to combating spam, as of late. The company is advocating a combination of technology, industry partnership, consumer education and regulation/enforcement as a way to reduce the growing volume of junk mail.

Microsoft has been fortifying the filtering software that it is building into its e-mail and instant messaging products. In April, it announced an industry partnership to fight spam, involving AOL Time Warner, Yahoo and Earthlink. And in May, Microsoft chairman Bill Gates sent a letter to a Senate committee holding spam hearings.