Yahoo unveiled today a new feature that will improve the security of the Web search experience. The new service, called SearchScan is basically a combination between Yahoo Search and McAfee’s SiteAdvisor technology.

When a users will conduct a search on Yahoo the site with security concerns, such as spyware, adware and other malicious software that can infect and damage a user's PC, will be eliminated from the results.

In addition, SearchScan will alert the users about the potentially risky sites by displaying a red warning sign in search results.

As explained on Yahoo SearchBlog, Search Scan will scan for three types of risks in Yahoo’s search index: Browser Exploits, Dangerous Downloads and Unsolicited Email.

The sites that contain browser exploits and can stealthily harm a user's computer or install malware simply by visiting will be eliminated. The sites that are identified with dangerous downloads will be labeled in the search results with a warning.

Also, SearchScan will alert users to scanned sites that send unsolicited emails or inappropriately share email addresses with third parties.

The new services is still in beta testing and during this period SearchScan displays McAfee alerts optimal for the Yahoo! Search user and does not include all McAfee SiteAdvisor red ratings.

While SearchScan will be on by default, users have control over how they use the feature. In preferences, users can choose to turn the feature off or choose to filter out all sites with warnings from their search results.

McAfee SiteAdvisor tests and rates, on an ongoing basis, nearly every trafficked site on the Internet for a wide variety of Web safety issues including spyware, adware, exploits, known phishing sites, excessive pop-ups and spam. Site Advisor's ratings are created by using patented advanced technology to conduct automated Web site tests.

According to the "The State of Search Engine Safety" study released last year by McAfee, about 4 per cent of search terms return results for websites that attempt to install spyware and other malicious code on users' computers.

In its study, McAfee estimated that US consumers make approximately 276 million monthly searches that lead to Web sites that could compromise online safety.

McAfee conducted the study by analyzing the first 50 search results returned by major search engines like Google, Yahoo and MSN for 2,300 popular keywords. The study found the highest ratio of risky sites in categories related to music and technology.

Google has launched a similar feature two years ago in partnership with StopBadware.org, an organization aimed at stopping the spread of malicious software.

If a site if flagged by StopBadware.org, a label will appear under its name in the Google’s search result page. If the users will click on the link, Google directs them to a page that provides more information and enables them to either continue to the page or go back to the search results.