NEW YORK -- Microsoft Corp. has filed five lawsuits aimed at halting the flow of malicious online advertising.

The Redmond, Wash., software maker filed the claims Thursday in Washington state court against five unknown individuals under the business names Soft Solutions, DirectAd, qiweroqw.com, ITmeter INC. and ote2008.info.

Microsoft's associate general counsel, Tim Cranton, announced the move in a blog post.

The company is accusing the defendants of spreading so-called "malvertisements," ads that can end up infecting computers with damaging software.

"For example," Cranton wrote, "ads may redirect users to a Web site that advertises rogue security software, also known as scareware, that falsely claims to detect or prevent threats on the computer."

A similar type of ad popped up last weekend on the Web site of The New York Times, one of the most popular news sites. It purported to scan visitors' computers for viruses and warned them to buy antivirus software.

Malvertisements may also introduce software that can steal personal data or take control of a computer, Cranton said.

Microsoft is asking a court in Seattle for damages as well as an order barring the advertisers from operating.

E-mail messages to ote2008.info and DirectAd were not immediately returned and phone numbers were not available for the companies. A phone call to ITmeter INC. went unanswered as did an e-mail message, while registration records for qiweroqw.com domain name had no contact information for the company. No contact information was available for Soft Solutions, which Microsoft said was separate from businesses operating by that name in Atlanta and France.