Starting Tuesday, there will be a few less Web sites popping up in Yahoo searches. That's because Yahoo plans to start filtering out malicious Web sites using McAfee's SiteAdvisor software, which warns Web surfers if they are about to visit a Web site that has been linked to spam, phishing, or malicious software.

SiteAdvisor can be downloaded as a plug-in to Firefox or Internet explorer, but Yahoo has been working since late last year to integrate McAfee's Web site rating technology into their search engine servers, according to Priyank Garg, a director of product management with Yahoo.

Web sites associated with malware will be dropped from search results altogether and Yahoo searchers will now see red warning labels warning them of sites that SiteAdvisor has linked with things like dangerous downloads or unsolicited e-mail.

Yahoo calls its version of the service SearchScan, and plans to turn it on by default for all users in the U.S., U.K., Germany, France, Italy, Spain, Canada, Australia and New Zealand.

The company will eventually roll SearchScan out in all of the countries it serves, with Asian and Latin American launches coming next, Garg said.

Garg estimated that the dropped malicious Web sites were getting as many as one million clicks from Yahoo searchers per day. "A lot of users were getting exposed to this without any knowledge," he said.

SearchScan is just the first of several new security features that McAfee and Yahoo have planned, said Tim Dowling, McAfee's vice president of McAfee's Web security group. "This is the beginning of a partnership," he said. "We see multiple opportunities to partner to work together to make the internet more secure."

But Yahoo will be the only search provider to use SiteAdvisor, he added. "This is an exclusive type of relationship."

Created in 2005, SiteAdvisor uses an automated Web site testing system to comb the Internet for suspicious sites. It was acquired by McAfee in 2006.