Yahoo Inc. and McAfee Inc. are joining to offer alerts about potentially dangerous Web sites alongside search results generated at Yahoo.com.
With the new security feature — slated to take effect Tuesday — people who search the Internet using Yahoo will see a red exclamation point and a warning next to links McAfee has identified as serving dangerous downloads or using visitors' e-mail addresses to send out spam.
Dangerous downloads can include "adware," which shows unwanted advertisements; "spyware," which secretly tracks users' keystrokes and other actions; and other malicious programs that can give criminals control over users' computers.
Yahoo and McAfee hope the move will quell users' anxiety about accidentally clicking on malicious links.
"Yahoo users have clearly told us that among the most important concerns for them are all these lurking threats on the Internet," said Priyank Garg, director of product management for Yahoo's search division. "They know the damage they can do but they don't know how to protect themselves."
Yahoo has decided to simply nuke the worst offenders — sites that attempt "drive-by downloads," or trying to automatically install malicious code on visitors' computers by exploiting coding flaws in their Web browsers.
If McAfee has identified a site as having employed such tactics, Yahoo users won't see the link at all.
"When a user gets a set of search results, there's really no indication of who's a good guy and who's a bad guy," said Tim Dowling, vice president of McAfee's Web Security Group. "You're really leaping off a platform of faith that you're clicking on a site that's safe and not one that's bad. And the bad guys really try hard to look good."
The companies declined to reveal the financial terms of the partnership.
The deal represents the latest attempt by Sunnyvale-based Yahoo to lure more search requests, snap out of its recent financial funk and steal advertising dollars from search leader Google Inc. as it tries to justify its rebuff of Microsoft Corp.'s $47.5 billion takeover bid.
Yahoo shares fell 15 percent Monday after Microsoft pulled out of merger talks over the weekend.
After Google, Yahoo operates the second most popular search engine among U.S. users, with 21 percent market share compared to Google's nearly 60 percent, according to data for March, the latest available, from comScore Inc.
The deal gives Santa Clara-based McAfee a way to expose more Internet users to its security software and tempt them to upgrade to premium versions.
McAfee also benefits from teaming with Yahoo because it can use Yahoo's search data to identify sites to examine for security holes and include within its products, McAfee's Dowling said.
The McAfee technology being used on Yahoo's site is a stripped-down version of McAfee's full SiteAdvisor technology that also is available for free directly from McAfee. It uses red, yellow and green icons to label safe and harmful sites. A premium version adds other features.
Billions of sites have harmful content, and the criminal hackers behind them try relentlessly to manipulate search rankings to boost their links and ensnare more victims.
Yahoo's Garg said the company was doing experiments to identify malicious sites and bar them from search results.
But he said "security is not Yahoo's forte" and McAfee's technology gives Yahoo the breadth and depth "many orders of magnitude greater than what we had before."